Obstructive Nephropathy



Obstructive Nephropathy


Sanjay Jain, MD, PhD

Helen Liapis, MD





Key Facts


Terminology



  • Acute or chronic damage to kidney due to obstruction of urine flow


Etiology/Pathogenesis



  • Many causes, congenital and acquired



    • Developmental defect


    • Neoplasia


    • Stones


  • UPJO most common cause


Clinical Issues



  • Chronic or repeated pyelonephritis


  • Flank pain


  • Hypertension


  • Renal failure (bilateral)


Macroscopic Features



  • Dilatation of pelvis (hydronephrosis), blunting of calyces


  • Marked loss of medulla, cortical thinning


Microscopic Pathology



  • Marked loss of tubules


  • Global and segmental glomerulosclerosis


  • Interstitial fibrosis, chronic inflammation


  • Dilation of collecting ducts


  • Dysplasia indicates congenital origin


Top Differential Diagnoses



  • Reflux nephropathy


  • Tubulointerstitial diseases







The typical features of chronic obstruction include dilation of the pelvis and calyces (hydronephrosis) image, loss of the medullary pyramids image, and secondary thinning of the cortex image.






A section of the medulla from a child with UPJO shows dilation of the larger medullary collecting ducts image due to increased urine back-pressure. The cortex is relatively spared image.


TERMINOLOGY


Definitions



  • Obstructive nephropathy



    • Damage to kidney due to urine flow obstruction


  • Hydronephrosis



    • Dilatation of renal pelvis due to functional or physical impediment to urine flow


ETIOLOGY/PATHOGENESIS


Causes



  • Physical obstruction



    • Stone


    • Tumors of the urinary tract



      • Prostate, bladder, ureter


    • Benign prostate hyperplasia (BPH)


    • External compression (tumors, pregnancy, retroperitoneal fibrosis, endometriosis, crossing vessels)


  • Functional obstruction



    • Developmental anomalies: Posterior urethral valves (PUV), ureterocele, ureteropelvic junction obstruction (UPJO), primary megaureter



      • UPJO is most common cause of obstructive nephropathy


Pathophysiology



  • Impediment to urine flow causes increase in back-pressure into collecting system and tubules


  • Increased back-pressure and retention of urine causes dilatation of collecting system and alterations in transporters and channels


  • Compression of renal parenchyma accompanies vascular compromise and inflammatory response


  • Cellular changes in interstitium and nephrons lead to varying degrees of scarring


  • Intrauterine obstruction during nephrogenesis can cause renal dysplasia


Animal Models



  • Unilateral ureteral obstruction (UUO)



    • Commonly used in rodents, marsupials


  • Genetic models



    • Provide evidence for functional defects rather than physical causes of obstructive nephropathy (Aqp2 mutations)


CLINICAL ISSUES


Presentation



  • Acute obstruction



    • Flank pain, nausea, and vomiting


    • Renal failure if bilateral


  • Chronic obstruction



    • Recurrent episodes of pyelonephritis


    • Hypertension


    • Renal failure if bilateral


Treatment



  • Surgical repair


  • Decompression


Prognosis



  • Prognostic criteria for congenital impediments to urine flow are not well defined; therefore, management criteria are debatable


  • Kidney failure may ensue if accompanied by dysplasia due to congenital obstruction


  • Correction of congenital obstruction may not resolve kidney damage; children should be followed into adulthood


  • High propensity to develop renal insufficiency in PUV patients


IMAGE FINDINGS


Ultrasonographic Findings



  • Dilated pelvis



MACROSCOPIC FEATURES


General Features



  • Dilatation of pelvis (hydronephrosis), blunting of calyces


  • Compression of the cortex


  • Irregular kidney surface due to scarring


  • Other anomalies or syndromes may be present: Hydronephrosis, small kidneys, duplicated collecting system, megaureter, hydroureter, dysplastic kidneys


  • Compensatory hypertrophy in contralateral kidney


MICROSCOPIC PATHOLOGY


Histologic Features



  • Glomeruli



    • Glomeruli relatively spared but eventually become globally sclerotic



      • Periglomerular fibrosis prominent


      • Global glomerulosclerosis, obsolescent glomeruli, glomerular cysts


      • Atubular glomeruli (cystic dilation of Bowman space)


    • Crescents seen rarely


    • Increased glomerular size in contralateral kidney


  • Tubules



    • Tubular atrophy, apoptosis


    • Thyroidization of tubules (end-stage atrophy)


    • Microcystic dilatation of distal nephron segments


    • Dilation of tubules may be more prominent in subcapsular collecting ducts


    • Rupture with leakage of Tamm-Horsfall protein


  • Interstitium



    • Fibrosis, diffuse


    • Mononuclear inflammation, plasma cells


    • Sometimes intense in sites of tubular rupture


    • Presence of cartilage or smooth muscle indicative of dysplasia



      • Segmental (lobar) or zonal (outer cortex) distribution


  • Vessels



    • Arterial medial hypertrophy and intimal fibroelastosis are indicative of hypertension


  • Pelvis and ureter



    • Pelvic dilatation, papillae effacement


    • Hypertrophy and dilation of ureter


    • Chronic inflammation mucosa of pelvis and ureter


Acute Obstruction



  • May have few pathologic findings


  • Interstitial edema, mild inflammation


  • Dilation of subcapsular collecting ducts


  • Dilated lymphatics contain Tamm-Horsfall protein

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Jul 7, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Obstructive Nephropathy

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