Which condition could cause post-renal azotemia?

Post-renal azotemia occurs when there is an obstruction in the urinary tract, leading to a build-up of nitrogenous waste products in the blood due to the inability of urine to flow freely from the kidneys. Urethral obstruction specifically refers to a blockage in the urethra, which can prevent urine from being excreted from the bladder. This obstruction can arise from various causes, such as urinary stones, tumors, or strictures, and results in increased pressure within the urinary system, subsequently leading to renal dysfunction and an increase in blood urea nitrogen (BUN) and creatinine levels.

The other conditions listed are associated with different forms of azotemia. For example, the primary loss of nephrons typically leads to prerenal azotemia due to insufficient filtering capacity of the kidneys but does not involve urinary obstruction. An infection in the kidney, such as pyelonephritis, might result in intrinsic renal damage and can also lead to prerenal or intrinsic azotemia rather than post-renal. Severe dehydration affects the ability of the kidneys to filter blood effectively, which is classically linked to prerenal azotemia as the body tries to conserve water, resulting in concentrated urine. Thus, ure