A 76-year old man has been unable to urinate for several days due to obstruction

Question

A 76-year old man has been unable to urinate for several days due to obstruction of the urethra by an enlarged prostate. He has high plasma creatinine (6 mg/dL), but shows no proteinurea. A catheter is placed in the bladder to relieve the obstruction. Over the next 24 h, the plasma concentration of creatinine falls to the baseline (1.3 mg/dL).

What was a primary reason for low GFR in the absence of catheter?

A protein leak through the filtration barrier. A primary glomerular disease. An increased oncotic pressure in the glomerulus. An increased hydrostatic backpressure (PBS). An increased hydrostatic pressure (PGC) in the glumerulus

Explanation / Answer

Answer - An increased hydrostatic backpressure (PBS).

Glomerular diseases damage the glomeruli, letting protein and sometimes red blood cells leak into the urine. This also leads to proteinurea

Protein leak present means it must be proteinurea

An increased hydrostatic pressure (PGC) in the glomerulus sends creatinine to the glomeruli.

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