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Renal / Genitourinary

Kidney Stones

Verified · Sep 2026

A kidney stone is a solid crystalline mass that forms in the urinary tract when urine becomes supersaturated with a stone-forming solute, causing severe colicky flank pain and hematuria when it obstructs the ureter.

The disorder behind renal colic, the writhing patient who cannot lie still, the 85% hematuria rule, the non-contrast CT, the collect-the-stone instruction — and the counter-intuitive fact that a low-calcium diet makes calcium stones worse.

What’s going wrong in the body

The normal physiology, where it fails, and why the body’s compensation backfires.

01 Supersaturation — the one step every stone shares

Patient-level, "a kidney stone is a solid piece of material that forms in the kidney from substances in the urine," ranging from "as small as a grain of sand" to "as large as a pearl." Clinically it is a common disease and getting commoner: lifetime prevalence affects about 1 in 11 people in the US, with a 2-to-1 male predominance, and prevalence has climbed from 3.8% in 1970 to 8.8% in 2010 and 10.1% in 2016. The reason prevention is not optional is recurrence — it approaches 50% at 10 years after a first stone, with a 26% median recurrence rate over 5 years in first-time formers.

Every stone, of every composition, begins at the same step: "supersaturation of the urine is the common denominator in all cases of renal calculi." Solute concentration exceeds solubility, crystals nucleate, and they aggregate. Most stones seed on a Randall plaque at the junction of the nephron’s collecting tubule and the renal pelvis, where calcium oxalate layers onto a calcium phosphate nidus. Understanding that one sentence organizes all of prevention, because there are only three ways to reverse supersaturation: dilute the urine, remove the solute, or change the pH.

Composition then sorts on chemistry — and pH is what sorts it. Calcium oxalate is 70–75%, the most common by far, forming in acidic urine (pH under 7.2). Calcium phosphate is about 10%, forming in alkaline urine and associated with hyperparathyroidism and renal tubular acidosis. Uric acid is 8–10%, and "only form[s] in acidic urine, usually with a pH less than 5.5" — it is radiolucent, invisible on plain film because it lacks calcium, and uniquely it can be dissolved by alkalinizing the urine rather than removed. Struvite is 7–8%, the infection stone, needing alkaline urine. Cystine is 1–2%, genetic, amber or tan, and notably resistant to shockwave therapy. Every one of those facts becomes a treatment decision later.

Supersaturation is the universal first step; urine pH then decides which stone forms. Because pH sorts the types, it also decides which stones can be dissolved rather than removed.

02 Why it hurts — and why the pain moves

The pain of renal colic is not the stone scraping anything. It comes from ureteral dilation and stretching of the renal capsule behind the obstruction. That mechanism produces the single most useful fact about severity: "the intensity of pain is related to the degree of obstruction, rather than the size of the stone." A 3 mm stone wedged perfectly can be agonizing; a large stone sitting in a calyx can be silent. Never reassure a patient on the basis of stone size, and never dismiss severe pain because the stone looked small on the scan.

Stones lodge at three narrowings, and knowing them explains the whole clinical course: the ureteropelvic junction, the pelvic brim at the iliac bifurcation, and the ureterovesical junction, "the narrowest portion of the ureter." Pain is referred along the T10 to S4 dermatomes, which is why it begins at the costovertebral angle and radiates "anteriorly and inferiorly toward the groin or testicle." Then it migrates: as the stone moves distally, "the patient may experience increasing lower urinary tract symptoms, such as dysuria, urinary frequency, urgency, or difficulty urinating." The symptom shift tracks the stone’s position — new bladder symptoms in a patient with known colic usually mean the stone has reached the ureterovesical junction, which is good news for passage and bad news for pain.

The timing is characteristic too. Pain peaks "within 90 to 120 minutes" and runs in three phases lasting up to 4 to 16 hours. And the observation that settles the differential costs nothing: the colic patient is "unable to find a comfortable position and may be writhing or pacing constantly, in contrast to patients with an acute abdomen, who generally prefer to remain still." A patient rolling around the stretcher is not exaggerating — restlessness is the classic behaviour, and stillness points somewhere else entirely.

03 The infection stone — a loop antibiotics cannot break

Struvite is magnesium ammonium phosphate mixed with calcium phosphate, called "triple phosphate" because it contains three cations — calcium, magnesium and ammonium — and one anion, phosphate. It is the only stone that is caused by infection rather than complicated by it, and it runs as a self-reinforcing loop.

A urease-producing organism splits urea into ammonia and carbon dioxide, yielding "two ammonium and one bicarbonate ion … for each urea molecule," which drives the urine strongly alkaline at pH above 7.2. Ammonium and magnesium then precipitate with phosphate — the stone forms. The same alkaline urine damages the protective cellular layer of the urothelium, a bacterial biofilm establishes itself on the stone surface, and the bacteria secrete polysaccharides that grow it further, eventually "taking the shape of the renal pelvis, infundibula, and calyces" — a staghorn calculus. Untreated, struvite stones "grow more rapidly compared to calcium-based stones" and may "fill up the entire collecting system."

Two practical consequences follow, and both are commonly got wrong. First, the organism is not the one you expect: Proteus produces urease in 100% of isolates, along with Klebsiella, Staphylococcus, Pseudomonas, Providencia, Serratia and Morganella — while only 1.4% of E. coli produce urease, so the commonest urinary pathogen is not the infection-stone pathogen. Second, the stone shelters the bacteria inside a biofilm, so antibiotics alone cannot win: "antibiotics alone are relatively ineffective in controlling urinary infections if infected struvite stone fragments remain," and "the optimal treatment for struvite stones is the complete surgical removal of all stone material." The stakes justify the surgery — "30% of patients treated conservatively without surgery ultimately died of sepsis or renal failure," and untreated struvite stones showed a 15-year overall survival of only 41%.

The struvite loop. The organism alkalinizes the urine, the alkaline urine builds the stone and damages the urothelium, and the stone then shelters the organism in a biofilm — which is why the cycle only breaks when every fragment is removed.

04 Obstruction plus infection — the emergency inside the diagnosis

Renal colic is painful; obstruction with infection is lethal. Pus trapped behind a blocked ureter is pyonephrosis, and the resulting obstructive pyelonephritis is "a potentially life-threatening condition… prompt surgical drainage of the renal pelvis is essential, as antibiotics alone are insufficient to resolve the condition." The numbers make the urgency concrete: delays in surgical decompression can raise the risk of death by about 30%, and postponing drainage beyond 2 days significantly increases morbidity and mortality.

The recognition criteria are specific enough to memorize. Patients with renal colic and "a fever of 100 °F (37.8 °C) or higher, significant leukocytosis (> 15,000 WBCs/mm³), pyuria, hypotension, or unexplained tachycardia should be considered at risk for urosepsis and obstructive pyelonephritis." Urosepsis itself is "characterized by symptoms such as hypotension, tachycardia (> 90 beats/min), tachypnea (> 20 breaths/min), pyuria, and leukocytosis (> 12,000/μL …)." The white count alone is not the trigger — fever, pyuria and the hemodynamics are. A raised count is common in ordinary colic: in one emergency-department audit of patients with a single ureteric stone, it was raised in about four of every five patients whose urinalysis showed only blood and whose cultures grew nothing, and the authors concluded that in most cases it is unlikely to reflect infection — antibiotics belong to signs of sepsis or a positive urinalysis. It was a small audit, and its authors note that a completely blocked kidney can leave the urine sample falsely negative, because the urine then comes only from the other kidney.

The treatment is drainage, not antibiotics and not stone removal. "The recommended treatment for patients with acute renal colic caused by an obstructing ureteral stone and signs of systemic infection, sepsis, or obstructive pyelonephritis is urgent drainage of the renal pelvis, either through cystoscopy with double J stenting or via percutaneous nephrostomy." In the critically ill patient, "percutaneous nephrostomy is the preferred method" — it "requires only minimal sedation and local anesthesia, minimizes manipulation of the infected renal unit." The stone is dealt with later, once the infection is drained and the patient is stable.

The emergency pathway. Fever, pyuria and hemodynamic change — not the white count alone — identify the obstructed, infected kidney, and the treatment is drainage rather than antibiotics or stone removal.

Causes & risk factors

Modifiable factors are teaching targets — the patient can act on them.

Inadequate fluid intake — the single modifiable driver of supersaturation; the target is a minimum of 2,000 mL of urine output daily modifiable High sodium intake — each 100 mEq rise in sodium raises urinary calcium by 50 mg, because sodium and calcium are reabsorbed together in the proximal tubule modifiable High animal-protein intake — all dietary meats, seafood, organ meats and poultry raise uric acid levels (plant proteins such as soy and lentils do not) modifiable High-oxalate foods — spinach (750 mg per half-cup serving), collard greens, rhubarb, chocolate, nuts, beets modifiable Sugar-sweetened sodas — one daily raises stone risk 22% to 33%; fructose specifically increases stone formation. (Higher coffee consumption correlates with lower incidence) modifiable Excess vitamin C — limit to under 1,000 mg/day, because the excess is converted to oxalate modifiable An overly restrictive low-calcium diet — it increases calcium stones, because gut calcium is no longer available to bind oxalate modifiable Metabolic drivers — hypercalciuria, hyperoxaluria, hyperuricosuria, hypocitraturia Diabetes, hypertension, gout, obesity and metabolic syndrome Family history increases incidence 2.5-fold; male sex carries a 2-to-1 predominance Urease-producing organisms — Proteus (100% urease-positive), Klebsiella, Staphylococcus, Pseudomonas, Providencia, Serratia, Morganella (note: only 1.4% of E. coli produce urease) modifiable Gastrointestinal disease causing dehydration and enteric hyperoxaluria — Crohn disease, irritable bowel syndrome, ileostomy, chronic diarrhea Genetic disorders — cystinuria and primary hyperoxaluria

Signs & symptoms

Each finding tied to the mechanism that produces it — and the triage it calls for.

Renal colic — acute, severe flank pain radiating to the abdomen and groin, testicle or labia early Expected
Why: Ureteral dilation and stretching of the renal capsule behind the obstruction, referred along the T10 to S4 dermatomes. Described as dull constant discomfort "interspersed with colicky episodes of intense, sharp pain." Pain intensity tracks the degree of obstruction, not the size of the stone.
Restlessness — the patient cannot find a comfortable position, writhing or pacing Expected
Why: The single bedside observation that separates colic from peritonitis: colic patients move constantly, "in contrast to patients with an acute abdomen, who generally prefer to remain still." A patient rolling around the stretcher is exhibiting the classic behaviour, not exaggerating.
Pain peaking within 90 to 120 minutes and running in three phases over 4 to 16 hours Expected
Why: The natural history of a stone engaging and then migrating through a ureteral narrowing. Knowing the arc prevents the mistake of reading a temporary easing as resolution.
Gross or microscopic hematuria in about 85% of patients Expected
Why: Mucosal trauma and congestion along the obstructed tract. The critical corollary is the other 15%: absent hematuria does not rule out a stone, so a negative dipstick never ends the workup in a patient with convincing colic.
Nausea and vomiting Hold & notify
Why: Shared autonomic innervation between the renal capsule, ureter and gut. Usually expected — but intractable vomiting is an admission criterion, because it prevents oral hydration and analgesia in a patient who needs both.
New dysuria, frequency, urgency or difficulty urinating in a patient with known colic Expected
Why: The stone has reached the ureterovesical junction, the narrowest part of the ureter. The symptom shift tracks the stone’s position — it means passage is close, and that the pain may intensify before it resolves.
Costovertebral angle tenderness with hypoactive bowel sounds Expected
Why: Local inflammation over the obstructed kidney and reflex ileus. Fever is explicitly "rarely" present without infection, which is why any fever in renal colic is treated as infection until proven otherwise.
Fever of 37.8 °C (100 °F) or higher with renal colic Report immediately
Why: The most important single finding on this page. Fever, pyuria, hypotension or unexplained tachycardia in a patient with an obstructing stone means obstructive pyelonephritis and urosepsis risk — and delaying decompression can raise the risk of death by about 30%.
Hypotension, heart rate above 90, respiratory rate above 20, pyuria and leukocytosis above 12,000/μL Report immediately
Why: The stated criteria for urosepsis — read together: the white count alone is not the trigger, because a raised count is common in colic without infection; the fever, the pyuria and the hemodynamics are.
New anuria coinciding with a known ureteral obstruction Report immediately
Why: Obstruction of a solitary functioning kidney or bilateral obstruction. It is an explicit indication for urgent urologic intervention — there is no renal reserve left to wait with.
Urine that smells bad or looks cloudy, with burning on urination Hold & notify
Why: The patient-facing version of pyuria and infection. Taught at discharge alongside fever and chills as the reasons to return rather than to wait out the pain.
Intractable pain or vomiting persisting beyond 3 days, or failure to pass a ureteral stone after 4 to 6 weeks late Hold & notify
Why: Both are listed indications for urologic intervention. Prolonged obstruction risks ureteral scarring and stricture, renal atrophy and permanent loss of function — so the waiting period has a defined end.

Diagnostics

Test In this disorder Normal
Non-contrast CT of the abdomen and pelvis It also supplies the two numbers that decide treatment: skin-to-stone distance and stone density in Hounsfield units. Pure uric acid stones read about 500 HU, calcium stones about 900 HU, and struvite 900 HU or less — which is how a radiolucent stone is characterized without an X-ray The gold standard — "the most sensitive and reliable test to diagnose urolithiasis"; identifies stone location and size plus hydroureter, hydronephrosis and ureteral edema —
Ultrasound Resistive index = (peak systolic velocity − end diastolic velocity)/peak systolic velocity; a value of 0.75 or above suggests obstruction. If ultrasound is nondiagnostic in pregnancy, options include "conservative measures and observation, low-dose CT imaging, magnetic resonance urography, or ureteroscopic surgery." The preferred first-line study in pregnancy, with no ionizing radiation; shows hydronephrosis and the resistive index Resistive index 0.7 or less is normal
Plain film (KUB) It may miss stones smaller than 5 mm and misses radiolucent types entirely. Uric acid stones are invisible on plain film because they lack calcium, so a uric-acid stone former is followed with ultrasound or CT — never with a KUB alone Screens for radiopaque stones only —
Urinalysis Crystal morphology names the stone: uric acid crystals are rhomboid or rosette and yellow or reddish-brown in acidic urine; struvite crystals have a "coffin-lid" morphology in alkaline urine above pH 7.2. The infection threshold that justifies antibiotics is at least 10 WBCs per high-power field (or more WBCs than RBCs), bacteriuria, or positive nitrites Hematuria in about 85%; assess also for crystalluria, pH and signs of infection (nitrites, leukocytes) —
Stone analysis "Any person who forms or passes a renal stone should undergo imaging and laboratory analysis of the stone," and "all stone material should be collected and sent for chemical analysis." Without it, prevention is guesswork: the diet, the urine-pH target and the drug all differ by stone type Composition of any passed or removed fragment — the result that determines every prevention decision that follows —
24-hour urine testing Never collected during the acute episode — obtain it once the stone event has been treated. Recommended for all pediatric stone formers, adults with significant renal failure or high surgical risk, and those with multiple stones, repeated stone surgery, a renal transplant, a solitary kidney or chronic diarrhea. Repeat after several months of therapy, then annually Identifies a metabolic abnormality in over 93% of stone formers. Optimal targets: volume 2,500 mL/24 h, specific gravity consistently 1.005 or less, calcium < 200 mg, oxalate < 25 mg/day, citrate about 640 mg or more, urine uric acid < 600 mg/24 h, sodium < 150 mg/24 h StatPearls (24-hour urine testing) Collection adequacy is confirmed by creatinine 20–25 mg/kg in men and 15–20 mg/kg in women per 24 hours
Acute laboratory panel Rising creatinine with obstruction is an indication for urgent intervention. Interpret the white count alongside fever, pyuria and hemodynamics — it supports the picture rather than making the diagnosis Urine hematuria, pH and bacteria; urine culture; BUN, creatinine, calcium, uric acid; CBC, CRP and coagulation profile European guideline panel, as reported by StatPearls —

Complications

Warning: Obstructive pyelonephritis, pyonephrosis and urosepsis Report immediately
Pus trapped behind a blocked ureter. Heralding cues: fever of 37.8 °C (100 °F) or higher, pyuria, hypotension, or unexplained tachycardia in a patient with an obstructing stone.
"Prompt surgical drainage of the renal pelvis is essential, as antibiotics alone are insufficient to resolve the condition." The cost of waiting is real: delays in decompression can raise the risk of death by about 30%, and postponing drainage beyond 2 days significantly worsens outcomes. Treatment is urgent drainage — cystoscopy with double-J stenting or percutaneous nephrostomy — with nephrostomy preferred in the critically ill because it needs only minimal sedation and local anesthesia and minimizes manipulation of the infected kidney. The stone itself is addressed after the infection is drained.
Warning: Struvite stones — not "just stones" Report immediately
"30% of patients treated conservatively without surgery ultimately died of sepsis or renal failure," and untreated struvite stones showed a 15-year overall survival rate of only 41%.
They cause "complete and persistent obstruction of the kidney causing permanent renal damage, pyonephrosis, sepsis, chronic pyelonephritis, and renal failure," and chronic irritation "can rarely result in squamous cell carcinoma of the renal pelvis," whose average 5-year survival is under 10%. Recurrence is the other trap: about 85% if residual fragments are left behind, falling to about 10% after complete extraction — which is why the goal is complete removal of every fragment rather than symptom relief.
Caution: Structural damage from prolonged obstruction
Hydronephrosis, pyelonephritis, forniceal (calyceal) rupture with urinary extravasation, perinephric abscess, ureteral scarring or stricture, renal failure or atrophy, chronic kidney disease, and staghorn calculi.
These are the reasons the waiting period for spontaneous passage has a defined end. Failure to pass a ureteral stone after 4 to 6 weeks is an indication for intervention, as is a rising creatinine with obstruction, obstruction of a solitary kidney, or bilateral obstruction. The kidney behind a stone is on a clock even when the patient is comfortable.
Caution: Procedural complications
After ESWL: renal colic in about 40%, steinstrasse ("stone street") in about 3% of which 6% need surgery, perirenal or subcapsular hematoma 1–4.6%, infection or bacteremia or sepsis about 10%, GI lesions 1.8%. After ureteroscopy: hematuria, mild UTI, stent discomfort, transient creatinine elevation.
The serious ureteroscopy complications are severe urosepsis, stone migration, ureteral perforation, stricture and avulsion, with risk driven by "positive preoperative urine cultures, higher body weight (body mass index), and older patient age." Overall ESWL stone-free rates approach 75%. After a procedure or while passing a stone, report pain that will not go away, fever and chills, vomiting, burning on urination, or little or no urine output.
Caution: Recurrence — the reason prevention exists
Recurrence approaches 50% at 10 years after a first stone, with a 26% median recurrence rate over 5 years in first-time formers.
Prevention success "will depend on the patient's willingness to follow a long-term course of treatment," including hydration compliance — which makes adherence teaching the highest-leverage nursing act on this page. A 24-hour urine collection identifies a treatable metabolic abnormality in over 93% of stone formers, so most recurrences are addressable rather than inevitable.

Medications for this condition

Why each class is prescribed here — every card links to its full pharmacology page.

NSAIDs First-line
Musculoskeletal · ibuprofen

First-line analgesia for renal colic, and the reason is mechanistic: the pain comes from prostaglandin-driven ureteral and capsular pressure, which is exactly what an NSAID reduces. Stated plainly by the sources: "NSAIDs are typically the first-line treatment for pain relief, as they are often as effective as, or even more effective than, opioids, while avoiding the complications associated with opioid usage." Parenteral options include ketorolac 15–30 mg IV or IM, or diclofenac 37.5 mg IV; ketorolac may also run as a continuous infusion at 3–5 mg/h. Two limits belong with the dose: ketorolac is for short-term use of under 5 days regardless of formulation, and the oral form is indicated only as a continuation of IV or IM therapy — it is not a stand-alone oral starter. An NSAID is also given immediately before shockwave lithotripsy to "minimize postoperative patient discomfort and decrease the requirement for post-procedure analgesics."
Opioid Analgesics High-alert
Nervous · morphine

The second-line and rescue role, not the opening move — which inverts what many patients and some clinicians expect for pain this severe. Morphine sulfate 0.1 mg/kg IV or IM or hydromorphone 0.02 mg/kg IV or IM "can be effective for analgesia, particularly when other treatments, such as ketorolac, have failed." The stated reason for the ordering is that opioids carry "unfavourable side effect profiles and have the potential for tolerance and misuse" while delivering no better analgesia than an NSAID in this specific pain. Practically, that means an opioid request in renal colic is a prompt to check whether an adequate NSAID has actually been given first.
Alpha-Adrenergic Antagonists (α-Blockers)
Autonomic · tamsulosin

Acutely, the alpha-blocker tamsulosin 0.4 mg orally daily is the most frequently used medical expulsive therapy (MET), relaxing distal ureteral smooth muscle so the stone can pass. The size band is larger than most people expect: pooled trial data show the benefit is concentrated in the larger ureteral stones — roughly 5 to 10 mm — with little gain for the smallest stones, which usually pass anyway, and the effect appears similar whatever the stone's position in the ureter. A stone that has not passed within 4 to 6 weeks, with or without this therapy, needs intervention. Silodosin has been shown superior to both tamsulosin and alfuzosin. Alpha-blockers are also used for the colic that follows lithotripsy and to ease ureteral stent discomfort.
Thiazide Diuretics
Renal · hydrochlorothiazide

For prevention: thiazides are the next step for hypercalciuria with recurrent calcium stones when diet alone is not enough, with indapamide and chlorthalidone (preferred for once-daily dosing) as the agents — and the effect size is striking, reducing median annual stone production from 2.94 to 0.05.

Beyond medications

  • Spontaneous passage is decided by size. Stones 4 mm or smaller have a 90–95% spontaneous passage rate; stones exceeding 7 mm are much less likely to pass; and stones larger than 10 mm will generally require surgery. These numbers set the plan and the conversation — a 3 mm stone earns fluids, analgesia and patience, while a 12 mm stone earns a urology referral on the first visit.
  • IV fluids are an adjunct, not a flush. "Intravenous fluid hydration is recommended as an adjunct to the initial treatment of acute renal colic," but "no evidence suggests that empiric fluids can help 'flush out' a stone." They exist to rehydrate the vomiting patient, not to move the stone — and telling a patient otherwise sets up a false expectation.
  • Urgent intervention is indicated for: an obstructing stone with infection (pyonephrosis), obstruction of a solitary kidney, bilateral obstruction, rising creatinine with obstruction, uncontrolled pain or nausea, sepsis, intractable pain, nausea or vomiting lasting more than 3 days, failure to pass a ureteral stone after 4 to 6 weeks, new anuria coinciding with the obstruction, and pregnancy unresponsive to conservative management. The infected-obstruction case is the most urgent of these: the recommended treatment is urgent drainage of the renal pelvis, by cystoscopy with a double-J stent or by percutaneous nephrostomy. Admission criteria: stones in a solitary kidney, severe kidney injury, infected stones, intractable pain or nausea, urinary extravasation, or sepsis.
  • Extracorporeal shockwave lithotripsy (ESWL) is "a viable first-line treatment" for non-staghorn renal and ureteral calculi under 2 cm; stones under 10 mm are excellent candidates, 10–20 mm need careful consideration, over 20 mm is generally not recommended. Success predictors: stone density under 1,000 HU and skin-to-stone distance under 10 cm; BMI over 30 kg/m² reduces success, and cystine, brushite and pure calcium oxalate monohydrate are relatively resistant. Absolute contraindications: pregnancy, severe or poorly controlled hypertension (a significant bleeding and perinephric-hematoma risk), untreated bleeding disorders, infected stones or untreated UTI, distal ureteral obstruction, and significant abdominal aortic aneurysm. More than two sessions "offer little additional benefit," and at least a week should pass between renal-stone treatments.
  • Ureteroscopy and shockwave lithotripsy are both first-line procedural options, chosen by stone size, location and composition. Shockwave lithotripsy is a viable first-line treatment for non-staghorn kidney and ureteral stones under 2 cm. Ureteroscopy with laser lithotripsy is favored for ureteral stones, especially in the lower ureter. Stenting is decided case by case: a stent is left when the ureter was injured or when bleeding, perforation, infection or significant fragments are a risk, because it "significantly reduces postoperative complications" at the cost of stent discomfort. In an uncomplicated case, a patient who was already stented before ureteroscopy may not need a new stent afterward. When one is placed, it is typically removed 5 to 7 days after a successful ureteroscopy.
  • Percutaneous nephrolithotomy (PCNL) handles renal pelvis stones over 2.5 cm and is "generally considered the gold standard for the surgical treatment of most large staghorn calculi," through a 24–30 Fr tract, with a stone-free rate of about 80% after PCNL alone. Struvite stones require complete surgical removal of all stone material, because any remaining fragment "can serve as a nidus for new stone formation" — and when shockwave therapy is used, "At least 50% of staghorn stone patients treated with SWL will require at least one more surgical treatment to become stone-free." For adult staghorn stones, shockwave therapy on its own clears the stone in only 18% to 67% of cases. Children do better: their staghorn stones are a smaller burden and their small bodies transmit the shock waves well, and pediatric series report clearance of 71–87.5% — yet the same review concludes that PCNL has become the accepted primary treatment in children, with shockwave therapy as the second option.
  • Follow-up imaging closes the loop. After stent removal, "a follow-up ultrasound or an x-ray (KUB) should be performed between 4 and 6 weeks later to rule out any residual fragments or silent hydronephrosis." After staghorn surgery, one urology review describes a renal ultrasound and plain film (KUB) at 4–6 weeks as a baseline, again at about 6 months, then every 6 months for the first 1–2 years and yearly once stable, plus a full metabolic work-up with a 24-hour urine study to guide prevention. Post-ESWL adjuncts that improve fragment clearance include mechanical percussion, alpha-blockers, and IV hydration with furosemide for renal stones.

Nursing considerations

The RN-specific layer — each action paired with the reason it matters.

Assessment & monitoring
Take the temperature on every patient presenting with renal colic, and treat a fever of 37.8 °C (100 °F) or higher as obstructive pyelonephritis until proven otherwise — alongside pyuria, hypotension and unexplained tachycardia.
Why: Fever is "rarely" present in uncomplicated renal colic, so its presence changes the diagnosis rather than adding to it. Delayed decompression of an obstructed, infected kidney can raise the risk of death by about 30%, which makes this the highest-stakes vital sign on the page.
Read the white count in context: a raised count is common in renal colic without infection, so the trigger is fever, pyuria and hemodynamics rather than the number alone — with extra caution in older, immunosuppressed or diabetic patients, who are more susceptible to infection.
Why: Treating every mild leukocytosis as sepsis floods the pathway with false positives and dilutes urgency; ignoring fever because the white count looks unremarkable misses the real one. The sourced criteria separate the two.
Observe how the patient holds themselves. Restlessness — writhing, pacing, unable to settle — is the classic colic behaviour, while a patient who will not move points toward an acute abdomen.
Why: This is a free diagnostic test performed from the doorway. It is explicitly contrasted in the literature, and it changes both the differential and how the reported pain severity should be interpreted.
Do not use stone size to predict pain, and do not use a negative urine dipstick to exclude a stone.
Why: Pain intensity "is related to the degree of obstruction, rather than the size of the stone" — and while about 85% of patients show gross or microscopic hematuria, 15% have none. Both errors send a genuinely obstructed patient home.
Track urine output, watching specifically for new anuria in a patient with a known obstruction, and follow the creatinine trend.
Why: New anuria coinciding with ureteral obstruction is an explicit indication for urgent intervention — it implies a solitary functioning kidney or bilateral obstruction, where there is no renal reserve to wait with. A rising creatinine with obstruction is the same message in slower form.
Note where the pain is and whether bladder symptoms have appeared.
Why: Pain referred along T10–S4 starts at the costovertebral angle and moves toward the groin; new dysuria, frequency and urgency mean the stone has reached the ureterovesical junction. The symptom shift tracks the stone, so the history is a rough localizer between scans.
Interventions & safety
Give the NSAID first — ketorolac 15–30 mg IV or IM — and treat an opioid request as a prompt to confirm an adequate NSAID has actually been given.
Why: NSAIDs are first-line because they are "often as effective as, or even more effective than, opioids" for this pain while avoiding opioid complications, and because they act directly on the prostaglandin-driven ureteral and capsular pressure that causes it.
Respect the ketorolac limits: short-term use under 5 days in any formulation, and oral ketorolac only as a continuation of IV or IM therapy.
Why: These are stated product limits rather than local custom. The oral rule in particular is often missed — ketorolac is not a stand-alone oral analgesic to start someone on at discharge.
Escalate for urgent drainage — not antibiotics alone and not stone removal — when obstruction and infection coexist.
Why: "Antibiotics alone are insufficient to resolve the condition." The decompression is the treatment: cystoscopy with a double-J stent, or percutaneous nephrostomy, which is preferred in the critically ill because it needs only minimal sedation and local anesthesia and minimizes manipulation of an infected kidney.
Give IV fluid to rehydrate the vomiting patient, and do not describe it as flushing the stone out.
Why: Explicitly, "no evidence suggests that empiric fluids can help 'flush out' a stone." Framing it as a flush sets an expectation that a patient will later judge the treatment against, and it distracts from the interventions that actually move stones.
Collect and send any passed or removed stone material for analysis, and make sure the patient knows to do the same at home.
Why: "Any person who forms or passes a renal stone should undergo imaging and laboratory analysis of the stone," because composition determines every prevention decision that follows — the diet, the urine-pH target, and the drug all differ between a calcium oxalate, a uric acid and a struvite stone.
Before shockwave lithotripsy, confirm there is no untreated UTI, no pregnancy, and no poorly controlled hypertension, and check the coagulation profile and antiplatelet or anticoagulant use.
Why: All four are absolute contraindications. Infected stones risk pyelonephritis, bacteremia and sepsis; severe hypertension is a significant risk factor for bleeding and perinephric hematoma. No antibiotics are required if the urine is sterile — the pre-procedure urinalysis and culture are what establish that.
Patient teaching
Teach the fluid target as urine output, not intake: at least 2,000 mL of urine daily with an optimal goal of 2,500 mL — which means drinking more than that. Offer the self-check: urine specific gravity should read 1.005 or less consistently.
Why: Dilution reverses supersaturation, the one step every stone shares. Framing the goal as output is what prevents a patient from believing that eight glasses a day is automatically enough, and the specific-gravity check turns an abstract target into something checkable.
Do not teach a low-calcium diet — teach normal dietary calcium taken with meals, and restrict sodium instead.
Why: This is the page’s central myth-buster. "An overly restrictive diet of dietary calcium can increase calcium nephrolithiasis due to a lack of intestinal calcium binding to other chemicals, especially oxalate" — calcium eaten with food binds oxalate in the gut so it is never absorbed. Sodium is the real lever: each 100 mEq reduction lowers urinary calcium by 50 mg.
Teach the rest of the sourced diet: sodium 1,500 mg daily optimal (no more than 2,300 mg), limit animal protein, avoid the high-oxalate list (spinach, collard greens, rhubarb, chocolate, nuts, beets), keep vitamin C under 1,000 mg/day, and avoid sodas and high-fructose drinks.
Why: Each item maps to a mechanism: sodium drives urinary calcium, animal protein raises uric acid, dietary oxalate and excess vitamin C raise urinary oxalate, and one sugar-sweetened soda daily raises stone risk 22% to 33%. Plant proteins such as soy and lentils do not carry the animal-protein penalty.
Recommend lemonade made from real lemon juice as an alternative beverage, and note that cranberry juice is not confirmed to help.
Why: Citrate inhibits stone formation, and real-lemon lemonade "is often suggested as an alternative to water as the primarily recommended beverage for all kidney stone formers." Naming the cranberry-juice caveat pre-empts a very common patient assumption.
After a procedure, teach what to expect and what to report. Expect hematuria (usually self-limiting) and colic after lithotripsy in about 40%, and, if a stent was placed after ureteroscopy, stent discomfort with the stent out in 5–7 days. Report pain that will not go away, fever and chills, vomiting, burning on urination, or little or no urine output.
Why: Separating the expected from the reportable prevents both unnecessary emergency visits for normal post-procedure hematuria and dangerous delays when a genuine complication — urosepsis, obstruction, steinstrasse — begins.
Tell patients with recurrent UTIs that they "might be harboring struvite and triple phosphate renal calculi," and that "treatment of the infection with antibiotics alone is not enough; complete surgical removal of the stone is needed."
Why: The biofilm on the stone shelters the organism, so repeated antibiotic courses treat the symptom and leave the reservoir. Saying this explicitly is what converts a frustrating cycle of recurrent infections into a reason to accept a surgical referral.

How a real nurse thinks

The clinical-judgment loop, worked for a typical presentation — reasoning, not reference.

  1. 1
    Recognize cues

    Two stories are running in this chart and they must not be read as one. Story one is uncomplicated colic: abrupt flank pain radiating to the groin, restlessness and pacing, gross hematuria, vomiting, CVA tenderness — all expected. Story two is what changed in the last hour: the temperature has risen from 37.2 to 38.1 °C, the heart rate is 112, the blood pressure has fallen from 134/82 to 98/58, the respiratory rate is 24, the urinalysis shows 40 WBCs/hpf with positive nitrites and many bacteria, the white count is 17,800, the creatinine has risen from 1.0 to 1.5, and the lactate is 2.8. The request for stronger analgesia is the loudest cue and the least important one.

  2. 2
    Analyze cues

    This is an obstructing stone plus infection — obstructive pyelonephritis with urosepsis, not colic that happens to hurt a lot. Check the criteria one by one. Fever of 37.8 °C or higher in renal colic: met at 38.1. Pyuria: met, with 40 WBCs/hpf, nitrites and bacteria — comfortably past the stated infection threshold of at least 10 WBCs/hpf with bacteriuria or positive nitrites. Hypotension and unexplained tachycardia: met. The urosepsis criteria line up too — heart rate above 90, respiratory rate above 20, pyuria, white count above 12,000. The white count of 17,800 is elevated, but it is the fever, pyuria and hemodynamics that make the diagnosis, not the number. The rising creatinine says the obstructed kidney is now failing. And note what the 7 mm size tells us. On its own it is an awkward stone: stones exceeding 7 mm are much less likely to pass spontaneously, yet a distal stone of this size is exactly where an alpha-blocker helps most — so in the absence of infection this would have been a medical-expulsive-therapy patient, not an immediate surgical one. The fever is what removes that option. Once obstruction and infection coexist, the plan is not expulsion and not stone removal; it is drainage.

  3. 3
    Prioritize

    The dangerous outcome is not the pain and not even the infection by itself — it is pus trapped behind an obstruction, where "antibiotics alone are insufficient", urgent drainage is the recommended treatment, and delays in decompression can raise the risk of death by about 30%. Priority one is escalation for urgent drainage of the renal pelvis, in parallel with blood cultures and antibiotics and fluid resuscitation. Priority two is the hemodynamics — a blood pressure that has fallen 36 points systolic in an hour. Priority three is analgesia, which matters and is not a competing emergency. The request for "something stronger" is answered on the way, not before the phone call — and the answer itself is worth checking, because the NSAID is first-line and he has had one dose.

  4. 4
    Generate solutions

    Escalate to urology and the attending immediately, framing this as an infected obstructed kidney rather than as colic with a fever. Anticipate urgent drainage by cystoscopy with double-J stenting or percutaneous nephrostomy — and know that if he decompensates further, percutaneous nephrostomy is the preferred route in the critically ill, because it needs only minimal sedation and local anesthesia and minimizes manipulation of the infected renal unit. Anticipate blood and urine cultures before antibiotics, empiric antibiotics, IV fluid resuscitation for the hypotension and lactate, and continuous monitoring. For pain, reassess the NSAID interval and anticipate an opioid as the sourced rescue — morphine 0.1 mg/kg or hydromorphone 0.02 mg/kg IV — "particularly when other treatments, such as ketorolac, have failed." What must not happen: admitting him for observation and pain control on the assumption that the stone will pass, or treating with antibiotics alone while awaiting a morning urology review.

  5. 5
    Take action

    Act and escalate together. Cultures drawn, large-bore access, fluids running, continuous monitoring, patient kept nil by mouth in anticipation of a procedure. The SBAR: "44-year-old with a 7 mm right UVJ stone and moderate hydronephrosis. In the last hour his temperature has gone from 37.2 to 38.1, heart rate 112, blood pressure fallen from 134/82 to 98/58, respiratory rate 24. Urinalysis shows 40 white cells per high-power field with positive nitrites and bacteria, white count 17,800, creatinine up from 1.0 to 1.5, lactate 2.8. This is an obstructed, infected kidney with urosepsis. Cultures are drawn and fluids are running. Requesting urgent urology for decompression — stent or nephrostomy — and empiric antibiotics now." The traps to name aloud: do not treat this as a pain problem, do not let the earlier mild leukocytosis explanation apply to a febrile hypotensive patient, and do not accept antibiotics alone as the plan.

  6. 6
    Evaluate

    Success in the next hours: the kidney is drained, blood pressure and heart rate respond to fluids and decompression, lactate falls, the fever settles, and the creatinine begins to recover. The stone itself is dealt with later, once the infection is controlled — that sequencing is the point. Before discharge, the prevention work begins: collect the stone for analysis if it is retrieved, because composition determines every subsequent decision; hydration teaching aimed at 2,000–2,500 mL of urine output daily with a specific gravity of 1.005 or less; sodium restriction rather than calcium restriction; and a 24-hour urine collection after the acute episode has resolved, never during it. He leaves with the report-immediately list — fever and chills, pain that will not go away, vomiting, cloudy or foul urine, burning on urination, no urine output — and with the understanding that a first stone carries a 26% median recurrence rate over 5 years.

Scenario — you’re the nurse

Work each question before revealing the answer. Rationales explain the wrong options too.

Emergency department · 2240, ninety minutes after arrival

A 44-year-old man with a first episode of right flank pain that began abruptly at 2100 and radiates to his right groin. He has vomited twice. He has been pacing the corridor and cannot stay on the stretcher. He received ketorolac 30 mg IV at 2130 with partial relief. A non-contrast CT at 2200 shows a 7 mm stone at the right ureterovesical junction with moderate hydronephrosis. He is now asking for "something stronger."

2240 vitals — T 38.1 °C (2130: 37.2 °C) · HR 112 · BP 98/58 (2130: 134/82) · RR 24 · SpO₂ 97% on room air
Assessment — restless, pacing, right costovertebral angle tenderness · skin warm and flushed · capillary refill 3 seconds
Urinalysis — large leukocyte esterase, positive nitrites, 40 WBCs/hpf, many bacteria, gross hematuria
Labs — WBC 17,800/μL · creatinine 1.5 mg/dL (baseline 1.0) · lactate 2.8 mmol/L
Imaging/chart — 7 mm stone at the right UVJ with moderate hydronephrosis · no prior stone history · analgesia: ketorolac 30 mg IV at 2130
Q1 Select all that apply
Which findings indicate that this is more than uncomplicated renal colic? Select all that apply.
  1. A. Temperature risen from 37.2 to 38.1 °C
  2. B. Blood pressure fallen from 134/82 to 98/58 with heart rate 112
  3. C. Urinalysis with 40 WBCs/hpf, positive nitrites and many bacteria
  4. D. Gross hematuria
  5. E. Restlessness and inability to stay on the stretcher
Reveal answer & rationale
Answer: A, B, C
Fever of 37.8 °C (100 °F) or higher in a patient with renal colic identifies risk of urosepsis and obstructive pyelonephritis, and fever is otherwise "rarely" present without infection (A). Hypotension with unexplained tachycardia is named in both the risk criteria and the urosepsis definition (B). Pyuria at 40 WBCs/hpf with nitrites and bacteriuria far exceeds the stated infection threshold of at least 10 WBCs/hpf with bacteriuria or positive nitrites (C). Gross hematuria (D) is expected — about 85% of stone patients have it — and restlessness (E) is the classic colic behaviour, explicitly contrasted with the stillness of an acute abdomen. Both are normal findings for this diagnosis and neither escalates it.
Q2 Multiple choice
The provider orders IV antibiotics and admission for pain control, planning a urology consult in the morning. The nurse’s best action is to:
  1. A. Carry out the orders and reassess the patient in two hours
  2. B. Escalate immediately, because an obstructed infected kidney requires urgent drainage and antibiotics alone are insufficient
  3. C. Request a repeat CT to confirm the degree of hydronephrosis before escalating
  4. D. Administer additional IV fluids to flush the stone past the obstruction
Reveal answer & rationale
Answer: B
The sourced rule is explicit: in obstructive pyelonephritis, "prompt surgical drainage of the renal pelvis is essential, as antibiotics alone are insufficient to resolve the condition," and delays in decompression can raise the risk of death by about 30% (B). Option A accepts exactly the delay the evidence warns against. Option C orders a test that would not change management — the CT already shows the obstructing stone and hydronephrosis — while the clock runs. Option D restates a myth this page kills outright: "no evidence suggests that empiric fluids can help 'flush out' a stone."
Q3 Put in order
Put the nurse’s first four actions in priority order:
  1. A. Administer the ordered analgesia and reassess pain
  2. B. Escalate to urology and the attending for urgent decompression
  3. C. Draw blood cultures and establish large-bore IV access with fluid resuscitation
  4. D. Document the vital-sign trend and the urinalysis findings
Reveal answer & rationale
Correct order: B → C → A → D
Escalation comes first because the definitive intervention — drainage of the obstructed, infected kidney — can only be arranged by the team, and every hour of delay carries measurable mortality (B). Cultures before antibiotics and fluid resuscitation for hypotension and a lactate of 2.8 follow immediately and are nurse-initiated (C). Analgesia matters and should not be neglected, but severe pain is not the competing emergency here (A). Documentation follows the care (D). Treating the pain first (A before B) is the intuitive error this case is built around — it is the ordering that turns a treatable obstruction into a septic one.
Q4 Multiple choice
At discharge, which statement by the patient indicates that prevention teaching has been effective?
  1. A. "I will cut out dairy and calcium so I stop forming calcium stones."
  2. B. "I will drink enough that I am passing about two and a half litres of urine a day, and cut back on salt."
  3. C. "I will drink cranberry juice every day since it prevents stones."
  4. D. "I will start a low-calcium, low-fluid diet to make my urine less likely to crystallise."
Reveal answer & rationale
Answer: B
The sourced targets are at least 2,000 mL of urine daily with an optimal goal of 2,500 mL — an output target, so intake must exceed it — and sodium restriction is the real lever, since each 100 mEq reduction lowers urinary calcium by 50 mg (B). Options A and D repeat the page’s central myth: restricting dietary calcium increases calcium stone formation, because gut calcium is no longer available to bind oxalate, which is then absorbed. Option D compounds it with fluid restriction, the exact opposite of the treatment. Option C names a beverage explicitly not confirmed as beneficial — the sourced recommendation is real-lemon lemonade, for its citrate.
Q5 Multiple choice
A colleague says the white count of 17,800 alone proved this patient was septic. The most accurate response is:
  1. A. "Correct — any leukocytosis in renal colic means infection."
  2. B. "The white count supports the picture, but it was the fever, pyuria and hemodynamics that made the diagnosis."
  3. C. "The white count is irrelevant in stone disease and should not have been ordered."
  4. D. "A white count above 12,000 is the single diagnostic criterion for urosepsis."
Reveal answer & rationale
Answer: B
The count supports the picture rather than establishing it — the decisive findings were the fever at or above 37.8 °C, the pyuria, and the hypotension with unexplained tachycardia (B). Option A would call sepsis from one number alone, although a raised count is common in colic without infection. Option C overcorrects: the count is part of the sourced acute panel, and 17,800 is above the sourced >15,000/mm³ urosepsis-risk threshold. Option D isolates one element of a multi-part definition — leukocytosis above 12,000/μL appears alongside hypotension, tachycardia above 90, tachypnea above 20 and pyuria, not instead of them.

Common questions

What causes kidney stones?
Common causes and risk factors include inadequate fluid intake — the single modifiable driver of supersaturation; the target is a minimum of 2,000 ml of urine output daily, high sodium intake — each 100 meq rise in sodium raises urinary calcium by 50 mg, because sodium and calcium are reabsorbed together in the proximal tubule, high animal-protein intake — all dietary meats, seafood, organ meats and poultry raise uric acid levels (plant proteins such as soy and lentils do not), high-oxalate foods — spinach (750 mg per half-cup serving), collard greens, rhubarb, chocolate, nuts, beets, sugar-sweetened sodas — one daily raises stone risk 22% to 33%; fructose specifically increases stone formation. (higher coffee consumption correlates with lower incidence), and others.
What are the early signs of kidney stones?
Early findings include Renal colic — acute, severe flank pain radiating to the abdomen and groin, testicle or labia.
Which findings should a nurse report immediately in kidney stones?
Report immediately: Fever of 37.8 °C (100 °F) or higher with renal colic, Hypotension, heart rate above 90, respiratory rate above 20, pyuria and leukocytosis above 12,000/μL, New anuria coinciding with a known ureteral obstruction, Obstructive pyelonephritis, pyonephrosis and urosepsis, Struvite stones — not "just stones". These signal deterioration that needs rapid intervention.
Should someone who forms calcium stones avoid calcium?
No — and the opposite is true. "An overly restrictive diet of dietary calcium can increase calcium nephrolithiasis due to a lack of intestinal calcium binding to other chemicals, especially oxalate." Calcium eaten with meals binds oxalate in the gut so the oxalate is never absorbed and never reaches the urine; take the calcium away and free oxalate is absorbed instead. The correct teaching is normal, moderate dietary calcium taken with food — and restricting sodium instead, since each 100 mEq reduction in sodium lowers urinary calcium by about 50 mg.
When does a kidney stone become an emergency?
When obstruction and infection occur together. A patient with renal colic and a fever of 37.8 °C (100 °F) or higher, pyuria, hypotension, or unexplained tachycardia is at risk for obstructive pyelonephritis and urosepsis — pus trapped behind the blockage. Antibiotics alone are insufficient; the treatment is urgent drainage of the renal pelvis by cystoscopy with a double-J stent or by percutaneous nephrostomy, the latter preferred in the critically ill. Delay matters in measurable terms: delays in decompression can raise the risk of death by about 30%, and postponing drainage beyond 2 days significantly increases morbidity and mortality.
Will a stone pass on its own, and what helps it?
It depends almost entirely on size. Stones 4 mm or smaller pass spontaneously 90–95% of the time; stones over 7 mm are much less likely to; and stones over 10 mm generally require surgery. What helps is medical expulsive therapy with an alpha-blocker — tamsulosin 0.4 mg daily. Note the size band, because it runs the other way from what people expect: pooled trials show the benefit is concentrated in larger stones, roughly 5–10 mm, not the tiny ones that pass anyway. So a 7 mm distal stone — one unlikely to pass on its own — is squarely a stone to try an alpha-blocker for. Add adequate analgesia (NSAID first, opioid as rescue) and hydration. What does not help is IV fluid given to "flush the stone out": "no evidence suggests that empiric fluids can help 'flush out' a stone." If a ureteral stone has not passed after 4 to 6 weeks, that is an indication for intervention.

Sources

Reviewed by Hae Suk Lee, RN

Educational summary for nursing students. Scenarios are fictional teaching cases. Always verify against current guidelines and your institution's protocols before acting in practice. Not medical advice.

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