4. Tubular & interstitial diseases Flashcards
Types of tubular & interstitial diseases
- Acute tubular necrosis
- Acute interstitial nephritis
- Acute pyelonephritis
- Chronic pyelonephritis
- Xanthogranulomatous pyelonephritis
- Renal tuberculosis
Definition of acute tubular necrosis
Clinicopathologic entity characterized by acute diminution of renal function & often morphologic evidence of tubular injury
Causes of acute tubular necrosis
- Ischemic causes:
- Shock, hemorrhage, major surgery, severe burns - Toxic causes:
- Endogenous products (haemoglobin released in hemolysis; myoglobin released in crush injuries & rhabdomyolysis)
- Drugs
- Heavy metals (lead, mercury)
- Organic solvents
Phases of acute tubular necrosis
1. Oliguric phase Results in: - Na+ & H2O overload - Metabolic acidosis - Hyperkalemia - Increased serum creatinine & BUN
- Polyuric phase
i. Clearance of sloughed off epithelial cells which allows for glomerular filtration rate to revert back to normal; however tubular epithelium is still not fully recovered, hence reabsorption of filtrate is impaired
ii. Results in:
- Dehydration
- Hypokalemia - Recovery phase
- Renal function recovering back to normal
Morphology of acute tubular necrosis
- Tubular epithelial cells show varying degree of swelling, vacuolation, flattening, sloughing, loss of PAS-positive brush border, necrosis
- Tubular dilation
- Contains eosinophilic casts (principally plasma proteins + Tamm-Horsfall protein, a urinary glycoprotein normally secreted by the cells of the thick ascending limb & distal tubule) - Interstitial edema
Pathological effects & complications of acute tubular necrosis
Acute renal failure
Definition of acute interstitial nephritis
Also known as acute tubulointerstitial nephritis
Causes of acute interstitial nephritis
- Drugs
- NSAIDs
- Antibiotics (methicillin, ampicillin, rifampicin)
- Diuretics (thiazides)
- Allopurinol
- Cimetidine - Toxins
- Metabolic causes
- Autoimmune
- Non-renal infections
Morphology of acute interstitial nephritis
- Interstitial edema
- Leukocytic infiltrate
- Focal tubular necrosis
Pathological Effects & complications of acute interstitial nephritis
Varying degree of renal function impariment
- Mild proteinuria
- Polyuria, nocturia
- RBCs, WBCs & eosinophils in urine (may be accompanied by fever & rash)
Definition of acute pyelonephritis
Acute infection of the kidney & collecting systems
Causes of Acute Pyelonephritis
- Typically coliforms
- Escherichia coli, Proteus, Klebsiella, Enterobacter - In immunocompromised:
- Polyomavirus, CMV, adenovirus
Routes of infection in pyelonephritis
- Ascending (retrograde) spread from lower urinary tract, predisposed by:
- Lower urinary tract obstruction (stone, benign prostatic hyperplasia, neoplasms etc)
- Vesicoureteric reflux
- Diabetes mellitus (increased susceptibility to infections; autonomic neuropathy can result in neurogenic bladder promoting urinary stasis)
- Pregnancy - Hematogenous spread
- Septicemic episode from distant
- Infective endocarditis
Morphology of acute pyelonephritis
- [Grossly]
- Cortical surface shows grey-white areas of inflammation & abscess formation
- Cut surface shows foci of abscesses within renal parenchyma
- Papillary necrosis (seen mainly in diabetics & NSAID use) – cut surface reveals tips or distal 2/3 of pyramids with areas of grey white/yellow necrosis - [Histologically]
- Patchy interstitial suppurative inflammation
- Tubular aggregates of neutrophils
- Tubular necrosis
Clinical features of acute pyelonephritis
- Fever, chills, malaise
- Flank tenderness & pain
- Signs of lower urinary tract infection:
- Dysuria
- Increased frequency of micturition - Pyuria (may have pus casts, which indicates renal involvement as casts are only formed in renal tubules)
- Detection of bacteria in urine (often >100000/ml)
Pathological Effects & Complications of acute pyelonephritis
- Acute renal failure
- Septicemia
- Pyonephrosis
- Perinephric abscess
- Papillary necrosis
- Mainly seen in diabetics & NSAID use
Definition of chronic pyelonephritis
Disorder in which chronic tubulointerstitial inflammation & renal scarring are associated with pathologic involvement of the calyces & pelvis; categorized into 2 main forms based on etiology
Causes of chronic pyelonephritis
- Vesicoureteric reflux (reflux nephropathy)
- Predisposes to recurrent renal inflammation & progressive scarring (most prominent at renal poles)
- Usually begins in childhood (congenitally short intravesical ureter – ureter takes a short route through the muscular wall of the bladder, hence rendering this physiological valve incompetent) - Obstruction (chronic obstructive pyelonephritis)
- Obstruction may be at any level below level of kidney, due to stones, BPH, neoplasms, etc
- Predisposes to recurrent renal inflammation & progressive scaring
Morphology of chronic pyelonephritis
- [Grossly]
- Irregular scarring
- Dilated, blunted, deformed calyces
- Flattened papillae - [Histologically]
- Atrophy of some tubules with dilation of others
- Dilated tubules filled with colloid casts, giving them a thyroid follicular appearance (thyroidization)
- Interstitial fibrosis & inflammation
- Periglomerular fibrosis
Pathological effects & complications of chronic pyelonephritis
Chronic renal failure
Definition of xanthogranulomatous pyelonephritis
Rare form of chronic pyelonephritis causes by Proteus spp. often in the setting of urinary tract obstruction
Morphology of xanthogranulomatous pyelonephritis
- Grossly:
- Enlarged kidney, replaced by yellow nodules with firm grayish white tissue - Histologically:
- Macrophages with vacuolated cytoplasm (foam cells)
- Giant cells, lymphocytes, plasma cells
Causes of renal tuberculosis
Hematogenous spread from pulmonary tuberculosis
- Occurs in 5% of cases of pulmonary TB
Morphology of renal tuberculosis
- Grossly:
- Initially: lesions in the medulla & papillae
- Later on: caseous foci enlarged in medulla & cortex to destroy the entire kidney - Histologically:
- Caseating granulomatous inflammation
