ABU Qualifying Exam cheat sheet

GFR = Kf × net filtration pressure; filtration stops when Bowman space pressure equals glomerular capillary pressure.

Inulin clearance is the reference for GFR; creatinine clearance overestimates GFR by tubular secretion.

Glucose reabsorption saturates at Tm ≈ 375 mg/min in men (transport maximum); glucose appears in urine above ~180 mg/dL plasma.

Countercurrent multiplier: thick ascending limb is water-impermeable and reabsorbs NaCl, generating a medullary gradient of up to 1200 mOsm/kg.

ADH acts on V2 receptors in collecting duct, inserting aquaporin-2; absence causes diabetes insipidus with dilute urine.

Aldosterone acts on principal cells via mineralocorticoid receptor, increasing ENaC and Na/K-ATPase activity.

Renal blood flow ≈ 20% of cardiac output (~1.1 L/min); cortex receives ~90% of renal perfusion.

Parathyroid hormone increases calcium reabsorption in distal tubule and inhibits phosphate reabsorption in proximal tubule.

Bladder compliance = Δvolume/Δpressure; normal compliance is high (>20 mL/cm H2O) so filling causes little pressure rise.

Hyperacute rejection is antibody-mediated (preformed antibodies) and occurs within minutes to hours; complement and neutrophils cause thrombosis.

Acute cellular rejection is T-cell mediated and responds to corticosteroids or anti-thymocyte globulin.

Chronic rejection is driven by donor-specific antibodies and manifests as transplant vasculopathy/glomerulopathy.

ABO and HLA compatibility determine donor-recipient pairing; HLA class I = A, B, C; class II = DR, DQ, DP.

Crossmatch positivity against donor lymphocytes contraindicates transplantation.

Tacrolimus inhibits calcineurin and IL-2 transcription; mycophenolate inhibits IMPDH and purine synthesis in lymphocytes.

Sirolimus (mTOR inhibitor) impairs wound healing and can cause proteinuria and hyperlipidemia.

Checkpoint inhibitors (anti-CTLA-4, anti-PD-1) increase antitumor immunity but risk autoimmune nephritis and colitis.

Central dogma: DNA → mRNA (transcription) → protein (translation); reverse transcriptase converts RNA to DNA.

VHL gene (3p25) mutation causes von Hippel-Lindau disease; loss of VHL stabilizes HIF and upregulates VEGF.

TSC1/TSC2 mutations cause tuberous sclerosis; mTOR pathway is constitutively active.

MET mutations occur in hereditary papillary renal cell carcinoma; MET encodes a tyrosine kinase receptor.

PCR amplifies DNA exponentially via denaturation, annealing, extension; quantitative PCR quantifies copy number.

Chromosomal translocation t(6;11) (TFEB) and t(X;1) (TFE3) define MiT family renal carcinomas.

BRCA1/BRCA2 mutations increase risk of prostate and renal cancers and are targets for PARP inhibitors.

BCR-ABL1 is the Philadelphia chromosome; imatinib is a tyrosine kinase inhibitor targeting it.

Primary hyperaldosteronism: elevated aldosterone with suppressed renin; screen with aldosterone-to-renin ratio.

Renovascular hypertension: renal artery stenosis causes renin release; ACE inhibitors may precipitate acute kidney injury in bilateral disease.

Pheochromocytoma: paroxysmal hypertension with headache, sweating, palpitations; diagnose with plasma metanephrines.

White-coat hypertension is elevated office pressure with normal ambulatory readings; masked hypertension is the reverse.

Resistant hypertension = uncontrolled on 3 drugs including a diuretic at optimal doses.

Malignant hypertension: severe pressure with papilledema or retinal hemorrhages; risk of thrombotic microangiopathy.

Hypertension in pregnancy: methyldopa, labetalol, and nifedipine are preferred; ACE inhibitors are contraindicated.

Renal artery stenosis may cause flash pulmonary edema and an abdominal bruit.

Delayed graft function: need for dialysis within first week after transplant; common in deceased-donor kidneys.

Warm ischemia time affects delayed graft function more than cold ischemia in some series; minimize both.

Living donor nephrectomy carries ~0.03% mortality and ~3-5% major complication rate.

BK virus nephropathy presents with rising creatinine and decoy cells; reduce immunosuppression as first step.

Calcineurin inhibitor toxicity causes afferent arteriolar vasoconstriction and striped cortical fibrosis.

Post-transplant lymphoproliferative disorder is associated with Epstein-Barr virus and intensified immunosuppression.

Kidney allocation uses HLA matching, waiting time, age, and sensitization (calculated PRA).

Donation after circulatory death grafts have higher rates of delayed graft function than brain-dead donors.

Erectile dysfunction is defined as inability to achieve or maintain erection sufficient for intercourse.

PDE5 inhibitors require nitric oxide (cGMP) pathway; contraindicated with nitrates due to hypotension.

Nocturnal penile tumescence testing distinguishes psychogenic from organic erectile dysfunction.

Intracavernosal injection of alprostadil (PGE1) is effective when oral agents fail.

Priapism: prolonged erection >4 hours; corporal aspiration and irrigation are first-line for ischemic priapism.

Peyronie disease: penile plaque causing curvature; associated with Dupuytren contracture.

Hypogonadism: low testosterone with symptoms; check morning total and free testosterone.

Ejaculatory dysfunction includes premature ejaculation and retrograde ejaculation (e.g., after bladder neck surgery).

Detrusor overactivity causes urgency and frequency; urodynamics show involuntary detrusor contractions during filling.

Detrusor sphincter dyssynergia: simultaneous detrusor contraction and sphincter activity, often with spinal cord lesions.

Stress urinary incontinence: leakage with increased abdominal pressure; midurethral sling is a common surgical treatment.

Post-void residual >150-200 mL suggests incomplete emptying; measure by ultrasound or catheterization.

Uroflowmetry: normal peak flow >15 mL/s in men; low flat curve suggests obstruction.

Overactive bladder first-line: behavioral therapy and antimuscarinics or beta-3 agonists (mirabegron).

Bladder outlet obstruction in men most often due to benign prostatic hyperplasia; treat with alpha blockers or 5-alpha-reductase inhibitors.

Neurogenic bladder from suprasacral lesions causes spastic bladder; sacral lesions cause areflexic bladder.

Complicated UTI: infection with fever, systemic symptoms, or structural abnormality; requires broader coverage and imaging.

Uncomplicated cystitis in women: nitrofurantoin, fosfomycin, or trimethoprim-sulfamethoxazole (based on resistance).

Pyelonephritis: flank pain and fever; obtain urine culture and consider CT if no improvement in 48-72 hours.

Prostatitis: acute bacterial causes dysuria, fever, and tender prostate; avoid prostatic massage in acute setting.

Four-glass test (Meares-Stamey) localizes chronic prostatitis to expressed prostatic secretions.

Epididymitis in young men: Chlamydia trachomatis and Neisseria gonorrhoeae; in older men, coliforms.

Emphysematous pyelonephritis: gas in renal parenchyma, common in diabetics; may require nephrectomy.

Genital ulcers: syphilis (painless), chancroid (painful), herpes (vesicles); obtain dark-field or PCR testing.

Interstitial cystitis/bladder pain syndrome: chronic pelvic pain with urgency and frequency; diagnosis of exclusion.

IgA nephropathy: mesangial IgA deposits; presents with hematuria after upper respiratory infection.

Goodpasture disease: anti-GBM antibodies cause pulmonary hemorrhage and rapidly progressive glomerulonephritis.

ANCA-associated vasculitis: granulomatosis with polyangiitis (c-ANCA/PR3), microscopic polyangiitis (p-ANCA/MPO).

Sarcoidosis can cause hypercalcemia and granulomatous interstitial nephritis.

Retroperitoneal fibrosis: fibrotic tissue encases ureters, causing hydronephrosis; associated with IgG4 disease.

Lupus nephritis: immune complex deposition; classify by ISN/RPS class I-VI on biopsy.

Amyloidosis: Congo red stain with apple-green birefringence; renal involvement causes proteinuria and nephrotic syndrome.

Primary hyperparathyroidism: elevated calcium with inappropriately normal or high PTH; most often due to adenoma.

Hypothyroidism causes decreased GFR and hyponatremia; myxedema can cause urinary retention.

Cushing syndrome: elevated cortisol; causes hypertension, hyperglycemia, and increased infection risk.

Diabetes insipidus: polyuria with dilute urine; central type responds to desmopressin, nephrogenic type does not.

SIADH: euvolemic hyponatremia with concentrated urine; treat with fluid restriction.

Conn syndrome (aldosterone-producing adenoma): hypertension with hypokalemia and metabolic alkalosis.

Pheochromocytoma: elevated catecholamines; alpha blockade before beta blockade to avoid hypertensive crisis.

Adrenal insufficiency: hyponatremia, hyperkalemia, hypotension; treat with glucocorticoid and mineralocorticoid replacement.

Calcium oxalate stones are most common; hypercalciuria, hyperoxaluria, and low urine volume are risk factors.

Struvite (magnesium ammonium phosphate) stones form with urease-producing bacteria (Proteus) and can form staghorn calculi.

Uric acid stones: radiolucent on plain film; treat with alkalinization of urine (potassium citrate).

Cystine stones: hexagonal crystals; treat with high fluid intake and urinary alkalinization.

Acute obstructing stone with infection is an emergency requiring decompression (stent or nephrostomy).

Noncontrast CT is the imaging modality of choice for suspected ureteral stones.

Shock wave lithotripsy is less effective for stones >2 cm and for lower pole stones.

Hyperoxaluria may be primary (genetic) or enteric (after bowel resection) and causes recurrent oxalate stones.

Renal trauma: most injuries are managed nonoperatively; absolute indication for surgery is hemodynamic instability.

Urethral injury: blood at meatus or high-riding prostate; obtain retrograde urethrogram before catheterization.

Bladder rupture: intraperitoneal rupture requires surgical repair; extraperitoneal may be managed with catheter drainage.

Testicular rupture: surgical exploration indicated when tunica albuginea is breached.

Renal pedicle injury: rapid deceleration; CT shows devascularized kidney; may require nephrectomy.

Ureteral injury: often iatrogenic during pelvic surgery; presents with urinoma or fistula.

Grade of renal injury by AAST scale (I-V) guides management; grade V includes main renal vein/artery avulsion.

Penile fracture: rupture of tunica albuginea during intercourse; emergent surgical repair.

Hydronephrosis on ultrasound is the first sign of obstruction; degree does not always correlate with severity.

Bilateral obstruction causes postrenal acute kidney injury with rising creatinine and oliguria.

Acute obstruction causes ipsilateral renal vasoconstriction and reduced GFR; relief restores diuresis.

Obstructive uropathy can cause hyperkalemic, hyperchloremic metabolic acidosis (type 4 renal tubular acidosis).

Postobstructive diuresis: large urine output after relief; monitor electrolytes and replace losses.

MAG3 diuretic renography distinguishes obstruction from nonobstructive dilation.

Ureteropelvic junction obstruction is the most common cause of congenital hydronephrosis in children.

Retroperitoneal fibrosis and pelvic malignancy are common causes of extrinsic ureteral obstruction.

Semen analysis: volume ≥1.5 mL, concentration ≥15 million/mL, motility ≥40%, normal morphology ≥4% (WHO criteria).

Azoospermia: absence of sperm; obstructive vs nonobstructive distinguished by FSH and testicular size.

Varicocele is the most common correctable cause of male infertility; left side predominates.

Klinefelter syndrome (47,XXY): small testes, gynecomastia, elevated FSH, azoospermia.

Obstructive azoospermia: normal FSH and testicular volume; may be treated with surgical sperm retrieval.

Y chromosome microdeletions (AZF region) cause severe oligospermia or azoospermia.

Female factor infertility includes ovulation disorders, tubal disease, and uterine abnormalities.

Intracytoplasmic sperm injection (ICSI) allows fertilization with a single sperm.

Renal cell carcinoma: clear cell (most common), papillary, chromophobe; clear cell associated with VHL.

RCC can cause paraneoplastic syndromes: hypercalcemia, polycythemia, and Stauffer syndrome (liver dysfunction).

Urothelial carcinoma: painless gross hematuria is the classic presentation; cystoscopy is diagnostic.

Bladder cancer risk factors: smoking, aromatic amines, cyclophosphamide, and pelvic radiation.

Prostate cancer screening: PSA with digital rectal exam; Gleason score determines grade group.

Testicular germ cell tumors: painless mass; alpha-fetoprotein and beta-hCG are tumor markers.

Wilms tumor: most common pediatric renal malignancy; presents with abdominal mass.

Upper tract urothelial carcinoma: often associated with Balkan endemic nephropathy and Lynch syndrome.

Ileal conduit: noncontinent diversion; urine drains to stoma bag; risk of metabolic acidosis and B12 deficiency.

Orthotopic neobladder: continent diversion to urethra; requires intact urethra and patient ability to catheterize.

Continent cutaneous reservoir (Indiana pouch): requires intermittent catheterization.

Metabolic complications of bowel diversion: hyperchloremic metabolic acidosis, especially with ileum and colon.

Jejunal conduit causes hyponatremic, hyperkalemic metabolic acidosis; rarely used.

Stoma complications: parastomal hernia, stenosis, and prolapse.

Upper tract surveillance after diversion is required because of reflux and risk of malignancy.

Ureteroenteric anastomotic stricture is a late complication causing hydronephrosis.

Vesicovaginal fistula: continuous urinary incontinence after pelvic surgery; diagnose with speculum exam and dye test.

Rectourethral fistula: passage of urine per rectum or stool per urethra; associated with prostate cancer treatment.

Obstetric fistula: prolonged obstructed labor causes pressure necrosis and fistula formation.

Colovesical fistula: pneumaturia and fecaluria; associated with diverticulitis.

Enterovesical fistula: recurrent UTI with mixed organisms; CT with oral contrast may demonstrate tract.

Urethrocutaneous fistula: complication of hypospadias repair or urethral stricture treatment.

Vesicouterine fistula: cyclical hematuria (menouria) and amenorrhea (Youssef syndrome).

Repair of vesicovaginal fistula requires adequate tissue health and may need interposition flap.

Hypospadias: ventral urethral meatus with chordee; avoid circumcision before repair.

Cryptorchidism: undescended testis; orchiopexy recommended by 6-18 months of age.

Vesicoureteral reflux graded I-V; low grades often resolve spontaneously.

Posterior urethral valves: most common cause of lower urinary tract obstruction in boys; presents with poor stream and hydronephrosis.

Antenatal hydronephrosis: most common cause is ureteropelvic junction obstruction.

Testicular torsion: acute scrotal pain with absent cremasteric reflex; surgical exploration is emergent.

Undescended testis increases risk of malignancy and infertility; early orchiopexy reduces but does not eliminate risk.

Bladder exstrophy: ventral abdominal wall defect with exposed bladder; staged reconstruction.

Kidney lies retroperitoneally at T12-L3; right kidney is lower due to the liver.

Renal artery divides into anterior and posterior branches; the posterior branch supplies the posterior segment.

Ureter has three anatomic narrowings: ureteropelvic junction, crossing the iliac vessels, and ureterovesical junction.

Prostate has peripheral, central, transition, and anterior zones; BPH arises in the transition zone.

Blood supply of ureter: upper third from renal artery, middle from gonadal/iliac, lower from vesical arteries.

External urethral sphincter is skeletal muscle under voluntary control; internal sphincter is smooth muscle.

Testicular blood supply: testicular artery, cremasteric artery, and artery to the vas deferens.

Lymphatic drainage of the testis is to para-aortic nodes; scrotal skin drains to superficial inguinal nodes.

Hyponatremia: assess volume status and urine osmolality; SIADH has high urine osmolality with euvolemia.

Hyperkalemia: treat with calcium gluconate for cardiac protection, insulin/glucose, and beta agonists; dialysis for refractory cases.

Hypokalemia causes metabolic alkalosis and can cause arrhythmias; replace with potassium chloride.

Hypercalcemia: treat with IV fluids, bisphosphonates, and calcitonin; parathyroidectomy for primary hyperparathyroidism.

Metabolic acidosis with normal anion gap suggests renal tubular acidosis or diarrhea.

Anion gap = Na − (Cl + HCO3); normal 8-12 mEq/L.

Hyperchloremic metabolic acidosis after urinary diversion is due to chloride reabsorption from urine.

Hypernatremia: free water deficit; correct slowly to avoid cerebral edema.