2017 Annual Meeting

SC24 -Bacterial Infection and the Kidney: Diagnostic Difficulties in Kidney Biopsies

March 9 2017, 1:00pm to 4:30pm


SC24 -Bacterial Infection and the Kidney: Diagnostic Difficulties in Kidney Biopsies

Session Credits: 3 CME and 3 SAMs

Faculty: Anjali A. Satoskar and Tibor Nadasdy. Ohio State University Wexner Medical Center, Columbus, OH

There has been a paradigm shift in the epidemiology and clinicopathologic diagnosis of glomerulonephritis associated with bacterial infection. Classic post-infectious/post-streptococcal glomerulonephritis is now rarely seen in the Western countries, and most cases are a consequence of active ongoing Staphylococcus aureus infections, affecting predominantly the elderly. These infection-associated glomerulonephritides are not postinfectious; but in most instances, the infection is still active and ongoing while the symptoms of glomerulonephritis evolve. Therefore we have introduced the term infection-associated glomerulonephritis (IAGN) which better describes this entity. Staphylococcus infection-associated glomerulonephritis may be misdiagnosed as IgA nephropathy or other forms of immune complex glomerulonephritis, including post-infectious glomerulonephritis. The distinction has important clinical and therapeutic implications, but unfortunately biopsy findings alone are often insufficient because of overlapping morphologic features. Another complicating factor is that the source of infection is frequently not clinically obvious (skin infections, osteomyelitis, deep-seated abscesses, tooth abscesses/granulomas and endocarditis). Staphylococcus infection may also mimic Henoch-Schnlein purpura (HSP). Endocarditis associated glomerulonephritis, especially in intravenous drug users, also shows similarities to (and subtle differences from) Staphylococcus IAGN. Using a case-based approach, we will discuss the wide spectrum of biopsy features seen IAGN, and important differential diagnostic considerations. Biopsy for native kidney pyelonephritis is infrequently performed, but interstitial nephritides mimicking acute pyelonephritis can be a diagnostic issue and will also be discussed. Bacterial infection can also directly affect the transplant kidney causing pyelonephritis in the renal allograft. Because of variable urine culture results, subdued clinical features in immunosuppressed patients, mixed nature of interstitial inflammation, zonal distribution of the interstitial inflammation and biopsy sampling issues, the biopsy diagnosis of acute pyelonephritis can be difficult and confused with that of acute rejection. The course will highlight these difficult diagnoses and briefly review new possible methods to distinguish them. The course is intended for a wide audience including residents, renal pathology fellows, and surgical pathologists involved in part-time or full-time renal pathology sign-out. Practical biopsy-based teaching points and diagnostic pitfalls will stimulate interest, highlight morphologic overlaps commonly encountered in the field of Renal Pathology and encourage more communication between pathologists and treating physicians.

Upon completion of this course, the participant should be able to

  1. Understand the difference between post-infectious glomerulonephritis and ongoing infection associated glomerulonephritis
  2. Recognize characteristic IgA dominant Staphylococcus-associated glomerulonephritis and its mimics IgA nephropathy and HSP nephritis
  3. Difficulties in the diagnosis of acute pyelonephritis in the renal allograft.


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