Kaplan USMLE Step 2: Older adult man unable to urinate

If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 2 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.  

A 71-year-old man comes to the physician because of problems with urination. He reports that over the past two weeks his urine stream has become weaker. Over the last 24 hours, he has been unable to urinate at all and is becoming extremely uncomfortable. There is no history of dysuria, hematuria, fever, or chills. He has a history of benign prostatic hyperplasia (BPH), for which he takes tamsulosin.

He takes diltiazem for hypertension and had a cholecystectomy 20 years ago. He denies any use of over-the-counter medications. His temperature is 37.4 ºC (99.3 ºF), pulse is 86 beats per minute, and blood pressure is 164/88 mmHg. He is in moderate distress. The abdomen is soft with lower abdominal distension and suprapubic discomfort on palpation and percussion. On digital rectal examination, the prostate is estimated to be 50 grams in size, nontender and without nodularity.

When an attempt is made to place a Foley urinary catheter, resistance is met and no urine comes out. Blood then begins to ooze from the urethral meatus. Which of the following is the best next step in management?

A. Insert bilateral percutaneous nephrostomy tubes.

B. Perform retrograde urethrogram.

C. Perform suprapubic tube placement.

D. Plan emergency ileal conduit creation.

E. Schedule emergent transurethral resection of the prostate.

The correct answer is C.

This patient has urinary retention with bladder outlet obstruction, the etiology of which is most likely his benign prostatic hyperplasia. Bladder drainage will relieve the patient's discomfort and prevent renal damage. Of the options provided, the least invasive and most expeditious choice is suprapubic (SP) tube placement, which can be achieved using a simple bedside percutaneous technique under ultrasound guidance.

The fact that the patient's bladder is distended will make the procedure easier. Once the bladder is located, a spinal needle is inserted 4–5 cm (about two finger-breadths) above the pubic symphysis under local anesthesia to confirm bladder depth and location. The catheter is then inserted in the same location.

Choice A: Percutaneous nephrostomy tubes are used to manage renal failure and bilateral hydronephrosis. Although this patient may have hydronephrosis, these tubes will only decompress the kidneys rather than the distended bladder, the source of this patient's discomfort.