VA Morning report pearls: Struvite stones and LBBB

Here are some round-up pearls from 2 great cases this week!


Case summary 1: On Monday, Jill presented the case of an elderly man with a history of obstructive struvite stones and Proteus bacteremia s/p nephroureterostomy tube, who presented with septic shock from recurrent/persistent struvite stones.

  • Interestingly, Proteus contributes to recurrent stone formation in 2 ways:
    • Urease splitting bacteria generate high urinary pH levels
    • The body can’t clear the urinary tract of the bacteria because they are embedded in the stones.
  • Other reasons to have alkaline urine: 
    • (1) urinary tract infection (Proteus and others)
    • (2) metabolic or respiratory alkalosis
    • (3) failure of acidification (renal tubular acidosis)
    • (4) ingestion (alkaline diet [a fad diet right now!], medications like sodium bicarbonate).
  • This is important, as alkaline urine can precipitate struvite and calcium phosphate stone formation
    • Acidify urine with cranberry juice or betaine
    • In contrast uric acid, cystine and calcium oxalate [most common in adults] stones precipitate in acidic urine (prevent with alkalinzation of urine via dietary changes or calcium citrate/K citrate

Here’s a great review on nephrolithiasis:  https://www.aafp.org/afp/2011/1201/p1234.html#afp20111201p1234-c1

  • A nephroureterostomy tube has both internal (via ureter) and external (via nephrostomy tube) drainage, so lack of external drainage does not necessarily indicate tube dysfunction.

Here’s a diagram for the visual-minded:

nephrostomy_catheter-fig_5-en


Case summary 2: At intern report, we discussed a patient who was post-op day #1 s/p an ankle fusion who developed chest pain and was found to have diffuse ST depressions and STE in aVR. This got us to talking more broadly about ACS and “STEMI equivalents.”

  • Moral of the story: new or presumed new LBBB may not predict ACS.
  • 2 retrospective studies looked at ~900 and ~300 patients with new or presumed new LBBB and concluded
    • Those patients with new or presumably new LBBB are a high-risk group (older, higher TIMI scores, more cardiomyopathy).
    • However only ~1/3 had acute MI, while the remaining patients had other cardiac or non-cardiac diagnoses

Here’s a Medscape article summarizing the literature on LBBB as a STEMI equivalent: https://www.medscape.com/viewarticle/753695_1

 

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