29 Sep 2020

8/19/20 Interstitial Nephritis

PGY2 Charles Shumaker presented a case of a 47 y/o female with no significant PMH presents with cyclical fevers x2 months and abdominal pain, nausea/vomiting x1 week.  The patient states that 2 months ago, she developed fever, malaise, fatigue and night sweats with decreased appetite.  She has been doing telehealth visits with an urgent care provider and has received multiple courses of augmentin, azithromycin and macrobid.  These treatments failed to alleviate her symptoms.  Denies recent travel or drug use.  Denies dysuria at this time but was recently treated for UTI.  Has noticed decrease in urine output.  Home medications include ibuprofen PRN, Tylenol PRN, ginko biloba and herbal tea.  Denies history of ethanol/tobacco/drug use.  Vital signs stable on presentation.  Exam without any significant findings.

CBC: WBC 11.5 > Hb 8.1/Hct 25 <Plt 541

CMP:

Na 137/K 5.3/Cl 102/HCO3 19/BUN 82/Cr 9.29 <Glucose 99 (*Of note, Cr was 2.04 a month prior to admission)

ALP 103>T.protein 6.8/Albumin 3.3/AST 13/ALT 16/Tbili <0.2/DBili <0.2

Coags:PT 15, INR 1.19

Infectious workup:

  • BCx negative x2
  • UCx negative
  • Lactate 1.2
  • Procal 0.26
  • HIV negative
  • RPR negative
  • Acute hepatitis panel negative
  • Anti-streptolysin O negative
  • Fungal serologies (aspergillus, blasto, histo, 1-3bD glucan, crypto) negative
  • TTE negative for endocarditis, EF 65-70%

Renal workup:

  • VBG 7.4/32/21/20, FiO2 21%
  • UA with 30 protein, negative blood, small leuk (0-3 WBC)
  • FeNa 5.3%
  • Urine protein/cr = 0.22/1137
  • PTH 68 (normal 15-65)
  • Vitamin D 25OH 36 ng/mL
  • SPEP and UPEP reveals no monoclonal protein bands
  • K/L: 89.5/87.1 = 1.03 (normal 0.26-1.65)
  • PLA2R negative
  • Cryoglobulin negative
  • Tox: negative for arsenic, lead and mercury
  • HbA1c 6%

Rheum workup:

  • ANA negative
  • dsDNA negative
  • C3 162 mg/L (normal 90-180)
  • C4 22.9 mg/dL (normal 10-40)
  • ANCA negative
  • Anti-GBM negative

Renal US: unremarkable.  Normal kidney size.

CT A/P with patchy heterogeneous enhancement of both kidneys, suggesting b/l pyelonephritis, alternatively, renal lymphoma could have a similar appearance.

PET/CT: There is a prominence of the renal silhouette with accompanying parenchymal hetermogeneity.  No definite evidence of focal lesions or areas of abnormal radiotracer activity are identified.

Renal Biopsy was performed which showed acute on chronic interstitial nephritis.

Treatment: Once the preliminary renal biopsy returned, patient was started on prednisone 60mg qday.  On outpatient follow up, patient in stable condition with Cr down-trending to 3.22 with steroid taper.

Take home points:

  1. Nephrotic syndrome differential:
    1. Renal limited disease: minimal change, membranous nephropathy, FSGS
    1. Systemic diseases: DM, HIV, amyloid, MM, SLE
  2. Nephritic syndrome
    1. Low complement
      1. Systemic: SLE, endocarditis, cryoglobulin
      1. Renal limited: MPGN, infection related GN
    1. Normal complement
      1. ANCA vasculitides
      1. Anti-GBM
      1. IgA vasculitis
  3. Triad of AIN (<10% seen): peripheral eosinophilia, fevers, rash
  4. Common offending agents of AIN: PPI, Penicillin, Cephalosporin, NSAIDs, Rifampin, TMP-SMX, Floroquinolones, Allopurinol, Mesalamine
  5. Initial treatment of AIN is stopping the offending agent.  Steroids can be used to treat if there is minimal interstitial fibrosis on renal biopsy.  Do not need renal biopsy to diagnose AIN if there is high suspicion.

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