Postrenale

Postrenale, or postrenal, refers to conditions in which urine flow is obstructed after it leaves the kidney, ultimately impairing renal function. The term is used in several languages in medical literature to describe obstruction-related kidney injury.

Causes include obstruction at the level of the ureter (urolithiasis, ureteral stricture, tumor), the bladder (incomplete emptying, neurogenic bladder, bladder outlet obstruction such as benign prostatic hyperplasia), or the urethra (urethral stricture, overflow). The obstruction increases hydrostatic pressure in the collecting system, decreases glomerular filtration, and can cause hydronephrosis and progressive kidney injury if not relieved.

Clinical features may include reduced urine output or anuria, flank or abdominal pain, and urinary symptoms; fever may occur if infection is present. Diagnosis relies on history and physical examination, urinalysis, and imaging such as ultrasound showing hydronephrosis; CT urography is useful when obstruction is uncertain. Additional tests may include renal function tests and, in complex cases, functional imaging or drainage studies.

Management centers on relieving obstruction promptly, using bladder catheterization for retention, ureteral stents or percutaneous nephrostomy for ureteral obstruction, stone removal, or treatment of the underlying cause. In some cases temporary dialysis may be required. Prognosis depends on the duration and severity of obstruction; promptly relieving the obstruction often allows recovery of renal function, while prolonged obstruction risks irreversible damage.

Postrenale AKI is one category of acute kidney injury, distinct from prerenal and intrinsic (intrarenal) causes, and requires timely recognition and intervention to prevent lasting renal impairment.