Postrenal

Question 1

What is the most common cause of postrenal azotemia?

Answer 1

BPH (Benign Prostatic Hyperplasia)

This is particularly true in older males, but can also be due to ovarian or cervical cancer impinging on the ureters.

Question 2

What does high creatinine in an old male patient typically indicate until proven otherwise?

Answer 2

BPH

This is a key point to remember for USMLE.

Question 3

Likely mechanism underlying old dude + high creatinine?

Answer 3

Increased Bowman capsule hydrostatic pressure

This is often the explanation for postrenal azotemia due to BPH

Question 4

What is the next best step in management for a patient with postrenal azotemia?

Answer 4

Insertion of catheter

This is preferred over antibiotics even if the patient has bacteriuria.

Question 5

What is the normal range for post-void volume?

Answer 5

<50 mL

A post-void volume of ~300-400+ mL indicates overflow incontinence.

Question 6

What should you check in an elderly male with high creatinine as a part of the management strategy?

Answer 6

Post-void volume

This is relevant but USMLE will not force a choice between this and catheter insertion.

Question 7

What condition (other than BPH, ovarian cancer, and cervical cancer) can lead to overflow incontinence and post-renal azotemia for USMLE?

Answer 7

Diabetic neurogenic bladder

This results from neuropathy affecting the detrusor muscle.

Question 8

What can hydronephrosis be seen as in patients with obstruction?

Answer 8

Large, dilated kidneys

This is a rare diagnosis in the context of postrenal azotemia.