Step 3 · 4–6%

Renal, Urinary & Male Reproductive

Kidney injury, CKD, sodium and potassium, stones, infections and the male patient.

Sodium, potassium & acid-base

Treat the ECG and severe symptoms first, then find the cause with osmolality, urine studies and the anion gap, and never correct sodium too fast.

Rules to know

Hyponatremia with seizures, coma or severe confusion → 100 mL of 3% saline over 10 minutes, repeat up to twice; aim for a quick 4–6 mEq/L rise
Chronic hyponatremia correction → raise sodium 4–8 mEq/L per day; never more than 10–12 in 24 h
High risk for osmotic demyelination → cap correction at 8 mEq/L per day; risk = alcohol use, malnutrition, hypokalemia, liver disease, sodium ≤105
Sodium rising too fast during a brisk water diuresis → stop saline, give D5W and/or desmopressin to bring it back down
First step in hyponatremia → serum osmolality: normal → lab artifact from lipids or protein; high → hyperglycemia or mannitol; low → true hypotonic hyponatremia
Hypotonic hyponatremia with urine osmolality <100 → primary polydipsia or low solute intake (beer, tea and toast); restrict water, add solute
Hypotonic hyponatremia, urine sodium <30, no edema → volume depletion; isotonic saline, then watch for overly rapid correction
Hyponatremia with edema from heart failure or cirrhosis → fluid restriction and loop diuretics; avoid saline
Euvolemic hyponatremia, urine osm >100, urine sodium >30, normal TSH and cortisol → SIADH; fluid restriction, then salt tablets with a loop diuretic, or urea
SIADH triggers → small cell lung cancer, CNS disease, pneumonia, SSRIs, carbamazepine, postoperative pain and nausea; find and remove the cause
Hyponatremia weeks after starting a thiazide → stop the thiazide; loop diuretics rarely cause this
Hypernatremia in a frail or confused patient → free water deficit from lack of access; correct chronic cases about 10 mEq/L per day with hypotonic fluid
Hyperkalemia → ECG first; peaked T waves, wide QRS or K ≥6.5 → IV calcium gluconate immediately to stabilize the myocardium
Hyperkalemia after calcium → shift with IV regular insulin plus dextrose and nebulized albuterol; bicarbonate only with metabolic acidosis
Hyperkalemia potassium removal → loop diuretic if urine flows, potassium binders (patiromer, sodium zirconium cyclosilicate), dialysis for renal failure or refractory cases
High potassium, normal ECG, hemolyzed draw or huge platelet count → pseudohyperkalemia (also very high WBC); repeat with a free-flowing sample
Hyperkalemia drugs to stop → ACE inhibitors, ARBs, spironolactone, TMP-SMX, NSAIDs, heparin and potassium supplements
Hypokalemia → check magnesium and replace it, or potassium will not stay up
Hypokalemia treatment → oral KCl when possible; IV no faster than 10 mEq/h peripherally, mixed in saline not dextrose, telemetry if severe
Urine potassium low with hypokalemia → GI loss or shift; high → renal loss from diuretics, vomiting with alkalosis, or mineralocorticoid excess
Metabolic acidosis → anion gap = Na − (Cl + HCO3), normal about 12; add 2.5 for each 1 g/dL albumin below 4
Expected compensation for metabolic acidosis → PaCO2 = 1.5 × HCO3 + 8 ± 2; a higher value means added respiratory acidosis
High anion gap acidosis → lactate, ketoacids, kidney failure, salicylate, toxic alcohols; check lactate, ketones, creatinine, salicylate level and osmolar gap
High anion gap with osmolar gap >10 → methanol or ethylene glycol; fomepizole and nephrology for dialysis
Gap rise much larger than the bicarbonate fall → hidden metabolic alkalosis too; much smaller → an added normal-gap acidosis
Normal-gap acidosis → urine anion gap: negative → diarrhea (ammonium excretion intact); positive → renal tubular acidosis
Normal-gap acidosis with high potassium in a diabetic → type 4 RTA (low aldosterone effect); stop offending drugs, loop diuretic, fludrocortisone if not hypertensive
Normal-gap acidosis, low potassium, urine pH >5.5, calcium phosphate stones → distal (type 1) RTA; oral alkali
Metabolic alkalosis with urine chloride <20 → vomiting, NG suction or past diuretics; isotonic saline plus potassium
Metabolic alkalosis with high urine chloride and hypertension → mineralocorticoid excess; normal BP → current diuretics, Bartter or Gitelman

Traps that cost points

Using hypertonic saline in asymptomatic chronic hyponatremia→ Hypertonic saline is for severe symptoms; asymptomatic chronic cases get cause-directed therapy and slow correction.
Giving normal saline for SIADH→ The salt is excreted while water is kept, so sodium may fall further; restrict fluid instead.
Not rechecking sodium once volume is restored→ Removing the ADH stimulus can unleash a water diuresis and overcorrection; check sodium every 2–4 hours.
Giving insulin before calcium when the ECG shows wide QRS→ Calcium protects the heart within minutes; shifting and removal come next.
Relying on sodium polystyrene sulfonate for emergent hyperkalemia→ It acts slowly and risks bowel necrosis; stabilize and shift first, then use newer binders or dialysis.
Repleting potassium without checking magnesium→ Low magnesium keeps the kidney wasting potassium; replace both.
Calling an acidosis normal-gap without correcting for low albumin→ Each 1 g/dL drop in albumin hides about 2.5 of anion gap.
Giving bicarbonate routinely for lactic acidosis in shock→ Restore perfusion; bicarbonate helps mainly with extreme acidemia plus kidney injury.

Acute kidney injury

In the Brain

Exclude obstruction and volume depletion, read the urine, stop the nephrotoxin, and dialyze for complications rather than a creatinine number.

Rules to know

AKI definition → creatinine up ≥0.3 mg/dL within 48 h, ≥1.5 times baseline within 7 days, or urine <0.5 mL/kg/h for 6 h
New AKI → review drugs and volume status, urinalysis with microscopy, bladder scan, and renal ultrasound to exclude obstruction
Older man with AKI and a distended bladder → urethral catheter first; ultrasound shows bilateral hydronephrosis
Large urine output after relieving obstruction → postobstructive diuresis; monitor electrolytes and replace fluid without matching every milliliter
BUN/creatinine >20, bland sediment, FENa <1% → prerenal; isotonic fluid if volume depleted
Prerenal-looking AKI in a patient on diuretics → use fractional excretion of urea; below 35% supports prerenal
Muddy brown granular casts, FENa >2% after hypotension, sepsis or toxins → acute tubular necrosis; supportive care, avoid nephrotoxins, dose drugs to GFR
AKI with rash, fever or eosinophilia after a new drug → acute interstitial nephritis (white cell casts; beta-lactams, PPIs, NSAIDs); stop the drug, steroids if slow recovery
NSAID combined with an ACE inhibitor and diuretic in an older patient → hemodynamic AKI; hold all three until recovery
Creatinine jump >30% soon after starting ACE inhibitor or ARB → look for bilateral renal artery stenosis or volume depletion; hold the drug
Contrast study needed with eGFR <30 or AKI → do the study; IV isotonic fluid around it; acetylcysteine and bicarbonate add nothing
Metformin with iodinated contrast → hold if eGFR <30 or AKI, resume after 48 h once kidney function is stable
Gadolinium with eGFR <30 or on dialysis → nephrogenic systemic fibrosis risk; use a lower-risk agent only when essential
Aminoglycoside for about a week → nonoliguric ATN with low magnesium and potassium; once-daily dosing and level monitoring
Amphotericin B → ATN, hypokalemia, hypomagnesemia and distal RTA; saline loading and frequent electrolytes
Tenofovir disoproxil with glucosuria, low phosphate and rising creatinine → proximal tubule (Fanconi) injury; switch to tenofovir alafenamide or another drug
Vancomycin with piperacillin-tazobactam → higher AKI risk; level-guided vancomycin and daily creatinine
High-dose acyclovir, methotrexate or sulfonamides → crystal nephropathy; hydrate well before and during
Long-term lithium → nephrogenic diabetes insipidus and CKD; creatinine, sodium and TSH about every 6 months
Dark urine, heme-positive dipstick without RBCs, very high CK → rhabdomyolysis; isotonic fluids for urine output around 200–300 mL/h
Rhabdomyolysis monitoring → potassium, phosphate, calcium (treat low calcium only if symptomatic) and compartment syndrome
Blue toes, livedo, eosinophilia, low complement after arterial catheterization → cholesterol emboli; supportive care and statin, no anticoagulation
AKI dialysis indications → refractory acidosis or hyperkalemia, dialyzable toxins, fluid overload despite diuretics, uremic pericarditis, encephalopathy or bleeding
Uremic bleeding before a procedure → desmopressin; dialysis treats the cause
Uremic pericarditis → urgent dialysis without heparin
After an episode of AKI → recheck kidney function at about 3 months; AKI raises later CKD risk

Traps that cost points

Ordering contrast CT before renal ultrasound in new AKI→ Ultrasound finds obstruction without contrast exposure; it is the first image.
Interpreting FENa in a patient on furosemide→ Diuretics raise urine sodium; fractional excretion of urea is the better marker.
Cancelling a needed contrast CT for fear of kidney injury→ Risk is mainly with eGFR under 30; a missed diagnosis costs more. Hydrate and proceed.
Starting dialysis because creatinine reached 6→ Dialysis is for complications like acidosis, potassium, overload, toxins or uremia, not a number.
Giving bicarbonate routinely in rhabdomyolysis→ No proven benefit; generous isotonic fluid is what protects the kidneys.
Replacing calcium aggressively early in rhabdomyolysis→ Calcium deposits in damaged muscle and rebounds high later; treat only symptoms or hyperkalemia.
Anticoagulating suspected cholesterol emboli→ Anticoagulation may worsen embolization; give supportive care and a statin.
Continuing an NSAID for pain in a patient with AKI→ NSAIDs cut renal perfusion; switch to acetaminophen.

Stones, urinary infections & incontinence

In the Brain

Image stones with low-dose CT, drain infected obstruction now, treat bacteriuria only when it counts, and match incontinence therapy to its type.

Rules to know

Colicky flank-to-groin pain with hematuria → noncontrast low-dose CT; ultrasound first in pregnancy, children, or to limit radiation
Renal colic pain → NSAIDs such as IV ketorolac first; opioids only for breakthrough pain
Distal ureteral stone 5–10 mm with pain controlled → tamsulosin to aid passage, strain urine, reimage in 4–6 weeks
Obstructing stone with fever or pyuria → emergency decompression by ureteral stent or nephrostomy plus antibiotics; remove the stone later
Stone >10 mm or not passed by 4–6 weeks → ureteroscopy or shock wave lithotripsy; large renal or staghorn stones → percutaneous removal
Staghorn stone with alkaline urine and Proteus → struvite; complete surgical removal plus antibiotics
After a first stone → fluids for ≥2.5 L of urine daily, normal calcium intake, less sodium and animal protein, stone analysis
Recurrent stones, a child with stones, or a solitary kidney → 24-hour urine metabolic study plus serum calcium and uric acid
Recurrent calcium stones with high urine calcium → thiazide; low urine citrate → potassium citrate
Stone invisible on x-ray but seen on CT, acidic urine, gout → uric acid stone; potassium citrate to alkalinize, allopurinol if urine uric acid is high
Healthy nonpregnant woman with dysuria and frequency, no discharge → uncomplicated cystitis; no culture needed: nitrofurantoin 5 days, TMP-SMX 3 days or fosfomycin once
Cystitis in a man → urine culture and 7 days of TMP-SMX or a fluoroquinolone; fever suggests prostatitis
Fever, flank pain and CVA tenderness, able to take pills → culture, then oral fluoroquinolone for 5–7 days or TMP-SMX for 14 days if susceptible
Pyelonephritis with sepsis, vomiting, obstruction or pregnancy → admit for IV ceftriaxone, broader if resistant organisms are likely
Pyelonephritis not improving after 48–72 h → CT or ultrasound for abscess or obstruction
Diabetic with severe pyelonephritis and gas in the kidney on CT → emphysematous pyelonephritis; IV antibiotics plus drainage or nephrectomy
Recurrent cystitis (2 in 6 months or 3 in a year) → confirm with cultures; vaginal estrogen if postmenopausal, then postcoital or daily prophylaxis
Asymptomatic bacteriuria → treat only in pregnancy or before urologic procedures that breach mucosa; not in older adults, diabetes or catheters
Nursing home resident with smelly urine, no fever or symptoms → no culture or antibiotics; hydrate and observe
Fever with a urinary catheter and no other source → replace a catheter in place >2 weeks, culture from the new one, treat 7 days (10–14 if slow response)
Preventing catheter infections → no indwelling catheter for incontinence alone; review need daily; intermittent catheterization beats indwelling
Candida in the urine of an asymptomatic catheterized patient → remove or change the catheter; no antifungal
First febrile UTI in a child 2–24 months → renal and bladder ultrasound; VCUG if ultrasound abnormal or febrile UTI recurs
New urinary incontinence → urinalysis, post-void residual, medication review, bladder diary; look for infection, stool impaction, diuretics, delirium
Leakage with cough, sneeze or lifting → stress incontinence; pelvic floor muscle training first, then pessary or midurethral sling
Sudden urgency with leakage → urge incontinence; bladder training and less caffeine, then a beta-3 agonist (preferred in older adults) or antimuscarinic
Constant dribbling with high post-void residual → overflow incontinence; stop anticholinergics and opioids, treat BPH, intermittent self-catheterization for neurogenic bladder
Bladder pain eased by voiding, frequency, sterile urine → interstitial cystitis; behavioral and diet changes, then amitriptyline or other agents

Traps that cost points

Treating asymptomatic bacteriuria in a catheterized or elderly patient→ It brings no benefit and breeds resistance and C difficile.
Sending a urine culture for every simple cystitis in a young woman→ Symptoms are enough; culture for recurrence, failure, pregnancy or complicated infection.
Using a fluoroquinolone for uncomplicated cystitis→ Keep fluoroquinolones for pyelonephritis; tendon, aortic and QT harms outweigh benefit in simple cystitis.
Treating an infected obstructing stone with antibiotics alone→ Infection behind an obstruction needs urgent drainage plus antibiotics.
Cutting dietary calcium in calcium oxalate stone formers→ Low calcium intake increases oxalate absorption and stones; keep normal calcium and cut sodium.
Prescribing oxybutynin to an 82-year-old with memory problems→ Anticholinergic load worsens cognition; a beta-3 agonist is preferred.
Placing an indwelling catheter to manage incontinence→ It invites infection; use scheduled toileting, pads or intermittent catheterization.
Choosing nitrofurantoin for pyelonephritis→ It does not reach kidney tissue levels; use a fluoroquinolone, TMP-SMX or beta-lactam.

Chronic kidney disease & dialysis

In the Brain

Stage by GFR and albumin, layer kidney-protective drugs, manage anemia and bone disease, and plan access and transplant early.

Rules to know

CKD definition → eGFR <60 or urine albumin-to-creatinine ratio ≥30 mg/g for over 3 months; stage by both GFR (G1–G5) and albuminuria (A1–A3)
Diabetes or hypertension → yearly eGFR and urine albumin-to-creatinine ratio; confirm a high ratio on 2 of 3 samples over 3–6 months
CKD with albuminuria → ACE inhibitor or ARB titrated to the highest tolerated dose; never the two together
Creatinine up ≤30% after starting ACE inhibitor or ARB → expected; continue and recheck potassium and creatinine in 1–2 weeks
CKD, eGFR ≥20, with albuminuria or heart failure → add an SGLT2 inhibitor, with or without diabetes, and continue it until dialysis
Diabetic CKD with albuminuria despite maximal ACE inhibitor or ARB → add finerenone if potassium is normal
Type 2 diabetes with CKD needing more glucose lowering → GLP-1 receptor agonist such as semaglutide, which also slows kidney decline
Blood pressure goal in CKD → systolic under 120 if tolerated, otherwise under 130/80
CKD at age 50 or older, not on dialysis → statin, with or without ezetimibe
Metformin in CKD → do not start at eGFR 30–45, reduce the dose if already taking it; stop below 30
Advanced CKD drug cautions → avoid NSAIDs, nitrofurantoin, magnesium or phosphate laxatives and enemas, morphine and codeine; reduce enoxaparin and gabapentin
Anemia of CKD → iron studies first; give iron if TSAT ≤30% and ferritin ≤500, then an ESA if hemoglobin stays below 10
On an erythropoiesis-stimulating agent → keep hemoglobin no higher than about 11.5; higher targets raise stroke, clotting and hypertension
CKD mineral-bone disease → high phosphate and PTH, low calcium and calcitriol; limit dietary phosphate and add binders such as sevelamer or calcium acetate
Rising PTH in CKD → correct vitamin D deficiency first; dialysis patients may add calcitriol or cinacalcet
Hypercalcemia with very high PTH after years on dialysis or after transplant → tertiary hyperparathyroidism; parathyroidectomy
Painful violaceous skin necrosis in a dialysis patient → calciphylaxis; sodium thiosulfate, wound care, stop calcium supplements and warfarin
CKD with serum bicarbonate below 18 → oral sodium bicarbonate to slow progression and protect bone
Recurrent hyperkalemia in CKD on RAAS blockers → low-potassium diet, diuretic, potassium binder; keep the kidney-protective drug
Nephrology referral → eGFR <30, albumin ratio >300 mg/g, decline >5 per year, red cell casts, resistant hypertension, recurrent hyperkalemia or hereditary disease
eGFR <30 and falling → protect nondominant arm veins (no PICC lines or draws); plan an arteriovenous fistula months before dialysis
eGFR <20 → refer for kidney transplant evaluation; preemptive transplant gives the best survival
When to start dialysis → symptoms such as uremia, fluid overload, potassium, acidosis or nutrition decline, usually at eGFR 5–10, not a fixed number
Fever in a hemodialysis patient with a catheter → cultures from catheter and periphery, vancomycin plus gram-negative coverage; remove catheter for S aureus, Pseudomonas or fungus
Cloudy effluent and abdominal pain on peritoneal dialysis → peritonitis if fluid WBC >100 with >50% neutrophils; intraperitoneal vancomycin plus gram-negative coverage
Kidney transplant recipient with rising creatinine → tacrolimus level, urinalysis, ultrasound with Doppler, then biopsy for rejection vs drug toxicity
Transplant patient on tacrolimus starting an azole, macrolide, diltiazem or rifampin → interactions shift levels; check and adjust tacrolimus
Kidney transplant recipient → yearly skin cancer exam and sun protection, plus age-appropriate cancer screening

Traps that cost points

Stopping an ACE inhibitor when creatinine rises 15%→ A modest rise reflects lower glomerular pressure; continue unless the rise exceeds 30% or potassium climbs.
Combining an ACE inhibitor with an ARB for more proteinuria reduction→ Dual blockade raises hyperkalemia and AKI without outcome benefit.
Stopping an SGLT2 inhibitor because eGFR dips after starting→ An early small dip is expected and part of its protective effect; continue.
Starting an ESA without checking iron→ Iron deficiency is common and blunts the response; replete it first.
Targeting a normal hemoglobin with an ESA→ Higher targets increase stroke, clots and death; stay at or below about 11.5.
Placing a PICC line in a patient heading toward dialysis→ It destroys veins needed for a fistula; choose another route such as a small-bore jugular line.
Using a sodium phosphate enema or bowel prep in CKD→ It can cause acute phosphate nephropathy and severe hyperphosphatemia; use polyethylene glycol.
Waiting for dialysis to begin before transplant referral→ Refer at eGFR under 20; preemptive transplant has the best outcomes.

Prostate, scrotum & male sexual health

In the Brain

Handle the emergencies first (torsion, priapism, Fournier), then make shared decisions on PSA and work stepwise through BPH and erectile dysfunction.

Rules to know

Sudden severe testicular pain, high-riding horizontal testis, absent cremasteric reflex → torsion; immediate surgical exploration without waiting for ultrasound
Torsion surgery → untwist and fix both testes; salvage is best within 6 hours, and manual detorsion is only a bridge
Upper-pole pain with a blue dot and a normal cremasteric reflex → torsed appendix testis; NSAIDs and rest
Gradual scrotal pain, tender posterior epididymis, pyuria → epididymitis; NAAT for gonorrhea and chlamydia
Epididymitis with STI risk → ceftriaxone 500 mg once plus doxycycline for 10 days; insertive anal sex → ceftriaxone plus levofloxacin
Epididymitis in an older man after instrumentation or with BPH → enteric organisms; levofloxacin for 10 days
Fever, perineal pain, tender boggy prostate → acute bacterial prostatitis; no prostatic massage, urine and blood cultures, TMP-SMX or fluoroquinolone for 2–4 weeks
Painless firm testicular mass → scrotal ultrasound; solid intratesticular mass → AFP, beta-hCG, LDH, then radical inguinal orchiectomy, never scrotal biopsy
Testicular cancer confirmed → CT of abdomen and pelvis for staging; offer sperm banking before further treatment
Undescended testis → refer by 6 months; orchiopexy by 18 months lowers but does not erase cancer risk
Painless scrotal swelling that transilluminates → hydrocele; adults need ultrasound to exclude tumor, infant hydroceles usually resolve by 1–2 years
Bag of worms above the testis, worse standing, left side → varicocele; repair for infertility with abnormal semen, pain, or adolescent testicular shrinkage
Right-sided, nonreducing or new varicocele in an older man → CT for a renal or retroperitoneal mass
Diabetic with painful, swollen, crepitant perineum → Fournier gangrene; emergency debridement plus broad-spectrum IV antibiotics
Painful rigid erection beyond 4 hours (sickle cell, trazodone, injections) → ischemic priapism; corporal aspiration and intracavernosal phenylephrine
Penile snap during intercourse with swelling and bruising → penile fracture; urgent surgical repair
Blood at the meatus after pelvic trauma → retrograde urethrogram before any Foley catheter
Lower urinary tract symptoms in an older man → history, symptom score, DRE and urinalysis; PSA only if the result would change care
Bothersome BPH symptoms → alpha-blocker such as tamsulosin first; warn about dizziness, retrograde ejaculation and floppy iris during cataract surgery
BPH with prostate >30–40 g or PSA >1.5 → add finasteride or dutasteride; full effect takes 6–12 months and PSA halves
BPH with retention, recurrent UTI, bladder stones, hematuria or obstructive kidney injury → surgery such as TURP
Acute urinary retention after an anticholinergic, decongestant or opioid → urethral catheter, start an alpha-blocker, voiding trial in a few days
Men 55–69 → shared decision about PSA screening; 70 and older → do not screen; start the discussion earlier for Black men or strong family history
Elevated PSA → repeat it after excluding infection, ejaculation or instrumentation, then prostate MRI before biopsy
Low-risk localized prostate cancer → active surveillance; higher risk → prostatectomy or radiation with androgen deprivation
Androgen deprivation therapy → baseline DXA with calcium and vitamin D; monitor glucose, lipids, weight and cardiovascular risk
Erectile dysfunction → cardiovascular risk check (lipids, glucose), medication review, morning testosterone if libido is low; PDE5 inhibitor first-line
PDE5 inhibitor and nitrates → contraindicated (severe hypotension); no nitrate within 24 h of sildenafil or 48 h of tadalafil
Infertile man with small firm testes, tall stature, high FSH and LH → Klinefelter syndrome; karyotype
After vasectomy → backup contraception until a semen analysis at 8–16 weeks shows no sperm

Traps that cost points

Ordering ultrasound before calling urology for classic torsion→ Imaging delays salvage; go straight to surgery when the picture is clear.
Biopsying a testicular mass through the scrotum→ It seeds the scrotum and alters lymphatic spread; radical inguinal orchiectomy diagnoses and treats.
Massaging the prostate in acute prostatitis to collect secretions→ It can cause bacteremia; culture the urine and blood instead.
Giving antibiotics for an isolated high PSA without prostatitis→ Antibiotics do not help without infection; repeat the PSA and proceed to MRI.
Reading PSA at face value in a man on finasteride→ 5-alpha reductase inhibitors halve PSA after 6–12 months; double it before interpreting.
Screening an 80-year-old with PSA→ Harms outweigh benefits after 70.
Prescribing sildenafil to a man who uses nitroglycerin for angina→ The combination causes profound hypotension; address angina and use nondrug ED options.
Treating priapism in sickle cell disease with fluids and transfusion alone→ After 4 hours ischemia damages tissue; aspirate and inject phenylephrine while giving supportive care.

Hematuria, proteinuria & glomerular disease

In the Brain

Confirm hematuria by microscopy, separate glomerular from urologic bleeding, and match the nephrotic or nephritic picture to its cause.

Rules to know

Dipstick positive for blood → microscopy; ≥3 RBC/hpf confirms hematuria; dipstick positive without RBCs → myoglobin or hemoglobin
Hematuria after exercise, during menses or with UTI → repeat urinalysis after the cause resolves before any workup
Gross hematuria in an adult, even on anticoagulants → CT urography and cystoscopy; anticoagulation does not explain it
Microhematuria at high risk (age ≥60, >30 pack-years, >25 RBC/hpf) → cystoscopy plus CT urography
Microhematuria at intermediate risk → cystoscopy plus renal ultrasound; low-risk young never-smoker → repeat urinalysis within 6 months or shared decision
Dysmorphic RBCs, red cell casts or proteinuria with hematuria → glomerular source; nephrology evaluation rather than cystoscopy
Flank mass, hematuria, new erythrocytosis or hypercalcemia → renal cell carcinoma; contrast CT, partial or radical nephrectomy
Pelvic fracture with gross hematuria → CT cystography; intraperitoneal bladder rupture → surgical repair, extraperitoneal → catheter drainage
Proteinuria on dipstick → quantify with a urine protein- or albumin-to-creatinine ratio; transient proteinuria with fever or exercise is benign
Adolescent with proteinuria only when upright → orthostatic proteinuria; compare first-morning and daytime samples, benign
Proteinuria >3.5 g/day, low albumin, edema, high lipids → nephrotic syndrome; adults usually need biopsy unless clearly diabetic
Child with nephrotic syndrome, normal complement, no hematuria → minimal change disease; prednisone without biopsy
Adult nephrotic syndrome with anti-PLA2R antibodies → membranous nephropathy; if antibody-negative look for cancer, hepatitis B, lupus or NSAIDs
Nephrotic syndrome with APOL1 risk, HIV, heroin use or severe obesity → focal segmental glomerulosclerosis
Diabetic with gradual albuminuria and retinopathy → diabetic kidney disease, no biopsy; active sediment or rapid decline → biopsy for another cause
Nephrotic older adult with large kidneys, heart failure or neuropathy → amyloidosis; free light chains, SPEP with immunofixation, fat pad or kidney biopsy
Nephrotic patient with sudden flank pain, hematuria or PE → renal vein thrombosis; CT or Doppler, then anticoagulate
Nephrotic syndrome supportive care → ACE inhibitor or ARB, loop diuretic, salt restriction, statin; anticoagulation if membranous with very low albumin
Nephritis weeks after strep throat or impetigo → post-streptococcal GN (1–3 weeks after throat, 3–6 after skin; low C3); diuretics and BP control
Post-streptococcal GN with low C3 beyond 8 weeks → biopsy for C3 glomerulopathy or membranoproliferative GN
Gross hematuria within days of an upper respiratory infection, normal complement → IgA nephropathy; ACE inhibitor or ARB, SGLT2 inhibitor if proteinuric
Child with leg and buttock purpura, joint and belly pain, hematuria → IgA vasculitis; supportive care, follow urinalysis and BP for 6 months
Creatinine rising over days with red cell casts → rapidly progressive GN; urgent ANCA, anti-GBM and complement, biopsy, pulse steroids if severe
Hemoptysis plus nephritis with anti-GBM antibodies → anti-GBM disease; plasma exchange, steroids and cyclophosphamide
Lupus with proteinuria >0.5 g/day or active sediment → kidney biopsy; class III–IV → steroids plus mycophenolate or cyclophosphamide, with hydroxychloroquine
Family history of hematuria with sensorineural hearing loss and eye changes → Alport syndrome; genetic testing, ACE inhibitor
Flank pain, hematuria, hypertension, large cystic kidneys, family history → ADPKD; ultrasound diagnosis, tight BP control with ACE inhibitor or ARB
ADPKD with family history of aneurysm or subarachnoid hemorrhage → MR angiography screening for intracranial aneurysm
ADPKD with fast-growing kidneys or falling GFR → tolvaptan with liver test monitoring

Traps that cost points

Attributing hematuria to warfarin and stopping the workup→ Anticoagulation unmasks underlying lesions; evaluate fully.
Ordering cystoscopy for hematuria with red cell casts→ Casts mean glomerular bleeding; check creatinine and proteinuria and involve nephrology.
Acting on a dipstick positive for blood without microscopy→ Myoglobin and free hemoglobin give false positives; confirm red cells microscopically.
Biopsying a child with classic nephrotic syndrome before steroids→ Most cases are minimal change; treat empirically and biopsy for steroid resistance or atypical features.
Prescribing antibiotics to treat post-streptococcal GN→ The infection has passed and the nephritis is immune-mediated; manage fluid and blood pressure.
Waiting for biopsy before steroids in severe rapidly progressive GN→ Nephrons are lost within days; start pulse steroids promptly when disease is severe.
Screening every ADPKD patient for brain aneurysm→ Screen those with family history of aneurysm or bleed, prior rupture, or high-risk occupations.