Acute tubular necrosis

Acute tubular necrosis
Classification and external resources
ICD-10	N17.0
ICD-9	584.5
DiseasesDB	11263
eMedicine	med/39 ped/28
MeSH	D007683

Acute tubular necrosis or (ATN) is a medical condition involving the death of tubular cells that form the tubule that transports urine to the ureters while reabsorbing 99% of the water (and highly concentrating the salts and metabolic byproducts). Tubular cells continually replace themselves and if the cause of ATN is removed then recovery is likely. ATN presents with acute renal failure (ARF) and is one of the most common causes of ARF.^[1] The presence of "muddy brown casts" of epithelial cells found in the urine during urinalysis is pathognomonic for ATN.^[2]

Classification

It may be classified as either toxic or ischemic. Toxic ATN occurs when the tubular cells are exposed to a toxic substance (nephrotoxic ATN). Ischemic ATN occurs when the tubular cells do not get enough oxygen, a condition that they are highly sensitive and susceptible to, due to their very high metabolism.^[3]

Diagnosis

Acute tubular necrosis is classified as a "renal" (i.e. not pre-renal or post-renal) cause of Acute renal failure. Diagnosis is made by a FeNA (fractional excretion of sodium) > 3% and presence of muddy casts in urinalysis. On histopathology, there is usually tubulorrhexis, that is, localized necrosis of the epithelial lining in renal tubules, with focal rupture or loss of basement membrane.^[4] Proximal tubule cells can shed with variable viability and not be purely "necrotic".^{[5][6][7][8][9]}40_75%

Toxic ATN

Toxic ATN can be caused by free hemoglobin or myoglobin, by medication such as antibiotics such as aminoglycoside and cytoxic drugs such as cisplatin, or by intoxication (ethylene glycol, "anti-freeze").

Histopathology: Toxic ATN is characterized by proximal tubular epithelium necrosis (no nuclei, intense eosinophilic homogeneous cytoplasm, but preserved shape) due to a toxic substance (poisons, organic solvents, drugs, heavy metals). Necrotic cells fall into the tubule lumen, obliterating it, and determining acute renal failure. Basement membrane is intact, so the tubular epithelium regeneration is possible. Glomeruli are not affected.^[1]

Ischemic ATN

Ischemic ATN can be caused when the kidneys are not sufficiently perfused for a long period of time (i.e. renal artery stenosis) or during shock. Hypoperfusion can also be caused by embolism of the renal arteries. Ischemic ATN specifically causes skip lesions through the tubules.^[2]

External links

• Photo at: Atlas of Pathology

References

1. ^ ^{a b} "Acute Tubular Necrosis (ATN)". Nephrology Channel. HealthCommunities.com. 2008. http://www.nephrologychannel.com/atn/index.shtml. Retrieved 2008-09-23. 
2. ^ ^{a b} Goldman, Lee; Cecil, Russell L. (2008). Cecil medicine. Philadelphia, PA: Saunders Elsevier. p. 705. ISBN 0-8089-2377-3. OCLC 191854838. 
3. ^ Goldman, Lee; Cecil, Russell L. (2008). Cecil medicine. Philadelphia, PA: Saunders Elsevier. ISBN 0-8089-2377-3. OCLC 191854838. ^{[page needed]}
4. ^ TheFreeDictionary > tubulorrhexis Citing: The American Heritage Medical Dictionary 2007
5. ^ Glynne PA, Picot J, Evans TJ (November 2001). "Coexpressed nitric oxide synthase and apical beta(1) integrins influence tubule cell adhesion after cytokine-induced injury". Journal of the American Society of Nephrology 12 (11): 2370–83. PMID 11675413. http://jasn.asnjournals.org/cgi/pmidlookup?view=long&pmid=11675413. 
6. ^ Glynne PA, Evans TJ (June 1999). "Inflammatory cytokines induce apoptotic and necrotic cell shedding from human proximal tubular epithelial cell monolayers". Kidney International 55 (6): 2573–97. doi:10.1046/j.1523-1755.2002.t01-1-00456.x. PMID 10354308. 
7. ^ Racusen LC (1998). "Epithelial cell shedding in acute renal injury". Clinical and Experimental Pharmacology & Physiology 25 (3–4): 273–5. doi:10.1111/j.1440-1681.1998.t01-3-.x. PMID 9590582. 
8. ^ Solez K, Racusen LC, Marcussen N, et al. (May 1993). "Morphology of ischemic acute renal failure, normal function, and cyclosporine toxicity in cyclosporine-treated renal allograft recipients". Kidney International 43 (5): 1058–67. doi:10.1038/ki.1993.148. PMID 8510383. 
9. ^ Racusen LC, Fivush BA, Li YL, Slatnik I, Solez K (April 1991). "Dissociation of tubular cell detachment and tubular cell death in clinical and experimental 'acute tubular necrosis'". Laboratory Investigation 64 (4): 546–56. PMID 1673163.