An elderly male presented with inability to void: Work-up for AKI revealed pre-renal etiology, likely a combination of hypovolemia and contrast induced nephropathy.
Teaching points:
-- New interns, you will find that one of the most common cross cover pages from RN's overnight is, "Mr./Ms. *** has not voided since X PM. What would you like me to do?" There are two possible scenarios...
-- 1. The patient cannot void - This is consistent with acute urinary retention. This is treated by decompression with foley catheter. Differential would include causes of obstruction (BPH, tumor), medications (anticholinergics, opioids, antipsychotics, antidepressants), or infection (prostatitis).
-- 2. The patient has noting to void- This is suggestive of oliguria/anuria from acute kidney injury. Differential would include pre-renal, intra-ranal, or post-renal etiologies.
-- The most useful test to differentiate these two scenarios would be a bladder scan or straight cath to quantify urine present in bladder. A bladder scan >300 mL would be concerning for acute urinary retention.
-- In our case, we found that there is minimal urine present in the bladder. Creatinine was diagnostic for acute kidney injury. The patient's elevated Bun:Cr ratio and urine osmolality as well as low urine sodium and FeNa were together suggestive of a pre-renal state.
-- Considering the recent contrast load 3 days prior, contrast induced nephropathy was the most likely diagnosis.
It's also quite possible sometimes overnight (cross-cover) that the patient is actually just sleeping. And, in fact, doesn't need to urinate. My first "diagnostic test" in these situations is always asking a patient to stand up (male) or sit down (female) and try to urinate. Obviously this patient had an issue...but how many people sleep all night without urinating? Most. And sometimes you can save the bladder scan.