Robbins - Pyelonephritis and UTI Flashcards
What is pyelonephritis and what structures does it affect?
inflammation affecting the tubules, interstitium, renal pelvis
What is the difference between acute and chronic pyelonephritis?
acute = bacterial infection
chronic = bacterial infection + other factors that predispose towards repeat acute infections
What organisms cause UTIs?
>85% caused by gram negative GI dwellers/fecal flora
Common bugs:
E. coli, Proteus, Klebsiella, Enterobacter
Fungal, viral and other bacterial cause problems too
How do microorganisms reach the kidneys?
- hematogenous spread from sepsis or distant infections
2 Ascending UTI or cystitis
What are the steps in an ascending infection causing pyelonephritis?
- colonization of distal urethra and introitus - adhesin and P-fimbrae interaction
- Urethra to bladder - catheters, lack of endogenous defenses
- Urinary tract obstruction and stasis of urine - residual urine
- Vesicouretal reflux - incompetent valve, congenital or bladder atony from spinal cord injury
- Intrarenal reflux - pulls urine into parenchyma/pyramids, esp at poles
What are the clinical features of acute pyelonephritis?
UT obstruction
Instrumentization/catheterization of urinary tract
Vesicoureteral reflex
Pregnancy - higher risk
gender and age - higher risk
Preexisting renal lesions
DM
Immunosuppression, immunodeficiency
What is the clinical picture of acute pyelonephritis?
Sudden onset of pain at CVA
systemic evidence of infection - fever, malaise
dysuria, increased frequency and urgency
urine has leukocytes/pyuria, but doesn’t differentiate between upper and lower UTI
leukocyte/pus casts = renal involvement
Use quantitative urine culture to Dx infection
What is the prognosis of acute pyelonephritis?
Benign, usu disappears aft a few days AB therapy
Bacteruria may persist for years with chronic pyelonephritis
What conditions make acute pyelonephritis more serious?
Unrelieved urinary obstruction
DM
immunodeficiency
Can lead to repeat septicemic episodes
combined with papillary necrosis can lead to renal failure
What virus can lead to interesting histological findings, and impacts kidney transplants?
polyomavirus
Reactivation in allograft immunosuppressed recipient can lead to nephropathy and rejection
Infects tubular epithelial cell nuclei
- nuclear enlargement and inclusions with LM
- inclusions have crystal lattics in EM
What is chronic pyelonephritis?
chronic tubulointerstitial inflammation and scarring involve calyces and pelvis
What conditions affect the renal calyces?
chronic pyelonephritis
analgesic nephropathy
What are the 2 forms of chronic pyelonephritis?
reflux nephropathy
chronic obstructive pyelonephritis
What is reflux nephropathy?
starts in childhood
UTI on top of congenital vesicoureteral reflux and intrarenal reflux
Reflux leads to scarring and atrophy, leading to renal insufficiency
- can be b/l or u/l
Vesicoureteral reflux can also cause problems in absence of infection - sterile reflux
What is chronic obstructive pyelonephritis?
recurrent infections on top of diffuse or localized obstructive leasions leads to renal inflammation and scarring
Leads to parenchymal atrophy and renal insufficiency
What are the morphological hallmarks of acute pyelonephritis?
Patchy interstitial suppurative inflammation
intratubular aggregates of neutrophils, neutrophilic tubulitis
tubular necrosis
- focal or wedge-sheped necrosis
How does the bacterial infection spread throughout the kidney with acute pyelonephritis?
Propelled into renal parenchyma with intrarenal/vesicoureteral reflux
collecting tubules –> tubular lumens –> interstitium –> abscess formation –>
tubules destroyed
(glomeruli usually spared)
What are 3 important complications associated with acute pyelonephritis?
Papillary necrosis
Pyenephrosis
Perinephric abscess
What would you see, histologically, with papillary necrosis? What diseases is it associated with?
Seen with DM, sickle cell disease, or urinary tract obstruction
u/l or b/l
pyramids have gray/white/yellow necrosis
- histologically -> ischemic coag necrosis, tubule outlines preserved
What happens in pyonephrosis?
Acute pyelonephrosis with total/almost complete obstruction high in urinary tract
Pus is unable to drain and fills renal pelvis, calyces, and ureter
What is perinephric abscess?
Acute pyelonephritis that has dissected through renal capsule into perinephric tissue
What clues does acute pyelonephritis leave behind after the infection has cleared?
Pus replaced with MOs, plasma cells, lymphocytes
Inflammatory foci replaced with scarring
Pyelonephric scar associated with inflammation, fibrosis, and deformation of the underlying calyx and pelvis
What are the morphological hallmarks of chronic pyelonephritis?
coarse, discrete corticomedullary scars overlying dilated, blunted, or deformed calyces and flattening of the papillae
- scars often in upper or lower poles
Dilated tubules with thyroidization/protein casts
Vessels have intimal thickening in scarred areas
HTN will cause arteriosclerosis, glomerular changes
What is xanthogranulomatous pyelonephritis?
Rare form of chronic pyelonephritis
- accum. of foamy MOs with plasma cells, lymphocytes, PMNs, giant cells
- assoc. with Proteus infections and obstruction
- lesions with large, yellowish orange nodules that look like renal cell carcinomas
What is the initial clinical presentation of chronic pyelonephritis?
back pain, fever, pyuria, bacteriuria
- gradual onset of renal insufficiency and HTN
Loss of tubular fxn - conc abililty - polyuria and nocturia
What are some important long-term sequelae associated with chronic pyelonephritis?
Some people can develop FSGS with significant proteinuria - bad sign
- several years aft scarring has occurred
- can progress to ESRD
Glomerulosclerosis is result of glomerular adaptations to loss of renal mass due to scarring. (renal ablation nephropathy)
