Check the pee Lab rounds Aug 7 th

Check the pee Lab rounds Aug 7 th, 2008 Kristian Hecht

Case 1 • 22 y female 3 day hx of dysuria, frequency and urgency. Afebrile. • Urine dip: +leuks, +nitrite, +RBC’s • Urinalysis: RBC 20 0 -5/hpf WBC 30 0 -5/hpf Epithelial Few 0/hpf Bacteria Many 0/hpf Casts None 0/hpf

Dipsticks in UTI • Multisticks measure Sp. gravity, p. H, glucose, nitrites, protein, leuks, rbc’s, bili, ketones • Leuks and nitrites are the most useful in suspected UTI

Dipsticks • WBC’s measured indirectly measuring leukocyte esterase activity • LE contained in neutrophils and macrophages • Sp 80 -90% • Sn 75 -96% • False –ve’s: high glc, high prot, tetracycline, keflex

Dipsticks • Nitrites produced by most Gm –ve uropathogens • Not produced by Pseudomonas or Enterococcus • Diet must contain nitrates to be +ve • Sn <50% • Sp >90%

Dipsticks • In children <12 y, when compared to microscopy, urine dips were equally as accurate Pediatrics 104: 54, 1999 • Less accurate in children <2 y • In adults with a typical UTI hx, some advocate for empiric tx with no further investigation based on a +ve dip

Microscopy • Urine spun at 2000 rpm for 5 min • Sediment is resuspended in remaining urine and examined + gram staining • WBC’s – >5/hpf in females, >2/hpf in males • Bacteria – >15/hpf

Case 2 • 18 y f, 3 d hx of dysuria, frequency and urgency • Dipstick +ve leuks, -ve for nitrite • Micro: RBC 1 0 -5/hpf WBC 30 0 -5/hpf Epithelial 0 0/hpf Bacteria 0 0/hpf Casts None 0/hpf

Microscopy • WBC’s – False negatives: dilute urine, leukopenia, partial treatment • Bacteria – Negative if: C. trachomatis, N. gonorrhea, HSV, S. saprophyticus – False –ve if: dilute urine, low bacterial load

Case 2 con’t • Further hx indicates recent unprotected intercourse with a new partner 10 d ago • Swabs taken • Teachable moment seized

Urine Culture • • Provides definitive diagnosis >105 CFU/m. L considered positive correlated with 95% likelyhood of infection >104 CFU/m. L correlated with only 50% likelyhood

Urine Culture • False +ve cultures are common due to contamination from uropathogens on the perineum and foreskin • Many studies show that urine culture is only useful when the diagnosis is uncertain or when there are host factors that make pathogen identification important

Groups in Which Urine Culture is Indicated 1. Children 2. Adult men 3. Immunocompromised patients 4. "Treatment failure" (recently completed course of antibiotics with persistent urinary symptoms) 5. Patients with symptoms in excess of 4 to 6 days 6. Elderly patients at risk for bacteremia 7. Toxic-appearing patients with signs and symptoms suggestive of pyelonephritis or bacteremia 8. Pregnant women 9. Patients with known chronic or recurrent renal infection 10. Patients with known anatomic urologic abnormalities 11. Patients in whom urinary tract obstruction is suspected (e. g. , stones, benign prostatic hypertrophy) 12. Patients with serious medical diseases, including diabetes mellitus, sickle cell anemia, cancer, or other debilitating diseases 13. Patients with alcoholism, drug dependence 14. Recently hospitalized patients 15. Patients taking antibiotics 16. Patients recently instrumented (e. g. , cystoscopy, catheterization)

Case 3 • 75 y male unresponsive, tachycardic, hypotensive, afebrile • Had complained of flank pain 24 h ago • Hx of BPH and mild UTI’s in past

Case 3 • While working this pt up for presumed urosepsis a urine was sent off… • Micro p. H 6. 0 RBC 10 0 -5/hpf WBC 2 0 -5/hpf Epithelial Mod - Necrotic renal tubular cells 0/hpf Bacteria Few 0/hpf Casts Many – epithelial casts 0/hpf Crystals Many - Oxalate mono/dihydrate 0/hpf

Case 3 • A neighbor comes by the ICU the next day and mentions that the pt had seemed depressed lately. • Pt also asked to borrow some antifreeze for his car 3 days ago…

Crystals • Crystals may be normally found in urine based on diet, concentration and p. H – Urate, oxalate • Pathologic crystals – Cholesterol – indicates marked proteinuria – Cystine – familial cystinuria – Drugs (Acyclovir, Amoxil, Cipro, Indinavir) • Can be implicated in cases of ATN

Casts • Form when urinary ‘Tamm-Horsfall’ proteins precipitate with low p. H or incr. concentration • Cellular debris can become entrapped in this precipitate • May help differentiate causes of acute renal failure and renal disease

RBC cast

Granular cast Waxy cast

Casts • Acute tubular necrosis – necrotic renal tubular epithelial cells (RTEC) – RTEC casts • Proliferative/Necrotic GN/vasculitis – erythrocytic casts • Rhabdomyolysis – myogolbin casts • Calcium oxalate crystals – ethylene glycol

Casts • Nephrotic syndrome – Proteinuria, lipuria with RTEC and fatty casts • Degree of hematuria can indicate underlying cause (mininmal change, membranous, focal segmental…) • Nephritic syndrome – Mod/Severe dysmorphic hematuria • RTEC casts and/or waxy casts

Other Casts • Hyaline – prerenal azotemia, normal • Granular – renal disease of any cause • Leukocytic – Pyelonephritis/acute interstitial nephritis

Take home goodies • Think about STI’s when the microscopy doesn’t fit with the story/dip • Don’t culture everyone • Crystals and casts can be useful in differentiating causes of ARF

Thanks!