Urinary tract obstruction (obstructive uropathy and hydronephrosis)

Acute kidney injury is a sudden rise in serum creatinine or fall in urine output from prerenal, intrinsic, or postrenal causes, defined and staged by KDIGO criteria. Management targets the underlying cause, corrects volume and electrolyte derangements, and escalates to renal replacement therapy for refractory hyperkalemia, acidosis, volume overload, or uremia.

Benign prostatic hyperplasia is age-related epithelial and stromal growth of the prostate transition zone causing bladder outlet obstruction and lower urinary tract symptoms in older men. Diagnosis rests on history, the AUA/IPSS symptom score, and a symmetrically enlarged, smooth prostate on digital rectal exam; management is staged from observation to alpha-1-blockers, 5-alpha-reductase inhibitors, and surgery.

Nephrolithiasis affects 7-11% of the US population, most often as calcium oxalate stones, and presents as colicky flank pain radiating to the groin with hematuria. Noncontrast CT confirms the diagnosis and stone size drives management: hydration, NSAID/opioid analgesia, and alpha-blocker expulsive therapy for stones under 10 mm, urologic intervention for larger, infected, or obstructing stones.

Urinary tract infection spans uncomplicated cystitis, presenting with dysuria, frequency, and suprapubic pain, through pyelonephritis, presenting with fever, flank pain, and costovertebral angle tenderness, most often from ascending Escherichia coli. Uncomplicated cystitis is treated empirically without culture using nitrofurantoin, trimethoprim-sulfamethoxazole, or fosfomycin, while pyelonephritis requires a pre-treatment urine culture and empiric fluoroquinolone or cephalosporin therapy, escalated to hospitalization and broader parenteral coverage for hemodynamic instability, obstruction, or failure to improve.

Neurogenic bladder is dysfunction of bladder storage or emptying caused by disease or injury of the central or peripheral nervous system, producing either a spastic, high-pressure bladder with urgency incontinence or an atonic, high-volume bladder with retention and overflow incontinence depending on lesion location. Diagnosis rests on the neurologic history and exam with urodynamic testing, and management is centered on a regular, low-pressure emptying regimen, most often clean intermittent catheterization, to protect renal function and prevent infection.

Prostate cancer is the most commonly diagnosed cancer in men, usually found through an elevated PSA in an asymptomatic patient, with risk stratified by PSA, Grade Group (Gleason score), and TNM stage. Localized low-risk disease is often managed with active surveillance, while higher-risk and metastatic disease require radiation, surgery, or androgen deprivation therapy escalated through castrate-sensitive and castrate-resistant phases.

Hyperkalemia is a serum potassium level above 5.0 mEq/L, most often from decreased kidney excretion, transcellular shifts, or excess intake, with levels above 6.0-6.5 mEq/L or any ECG change constituting a medical emergency from the risk of fatal arrhythmia. Treatment sequences cardiac membrane stabilization with calcium, transcellular potassium shifting with insulin/dextrose and albuterol, then definitive potassium removal with binders, diuretics, or dialysis.

Renal tubular acidosis is a normal anion gap metabolic acidosis caused by impaired renal bicarbonate reabsorption (type 2, proximal) or impaired distal acid excretion (type 1, hypokalemic distal, or type 4, hyperkalemic distal from aldosterone deficiency or resistance). The urine anion gap, serum potassium, and urine pH distinguish the three types, which are treated respectively with alkali replacement plus a thiazide, potassium citrate, and correction of the underlying cause plus mineralocorticoid replacement when appropriate.