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Pathology of Tubular Diseases
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MINA, MINA, MIRAL Page 1 of 5
EXAM OS 214: Nephrology Lec 08: Pathology of Tubular Diseases Sonya Chicano, MD
February 18, 2015
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I. ACUTE TUBULAR NECROSIS
A clinico-pathologic entity characterized by destruction of tubular epithelial cells and acute suppression of renal function
Also known as Acute Kidney Injury (AKI)
Acute Tubular Necrosis (ATN) is fairly common
Common in hospital setting, patients present with complicated history and clinical course
Eventually the patient will develop oliguria or anuria
Most common cause of Acute Renal Failure (ARF) o Rapid reduction of renal function and renal flow, falling
within 24 hours to less than 400 mL per day
Presents with increased serum creatinine, much like glomerular and vascular disease
We must determine if it is a glomerula/vascular/tubulo-interstitial disease.
A. Causes of Acute Tubular Necrosis 1. Ischemia due to decreased or interrupted blood flow
o Polyarteritisnodosa o Malignant Hypertension o Hemolytic-uremic syndrome o Decreased effective circulating blood volume
2. Direct Toxic injury to the tubules (Proximal Tubule affected) o Drugs o Radiocontrast dyes o Myoglobin o Hemoglobin o Radiation
3. Acute tubulointerstitial nephritis o Hypersensitivity reaction to drugs
4. Disseminated intravascular coagulation (DIC) 5. Urinary obstruction
o Tumors o Prostatic Hypertrophy o Blood Clots
B. Ischemic Acute Tubular Necrosis
Focal tubular epithelial necrosis with skip areas (destruction is patchy) since it depends on blood supply
Interstitial edema
Epithelial regeneration – some cells appear reactive
Rupture of Tubular Basement Membrane (TBM) and occlusion of tubular lumina by casts
May manifest histologically as: o Sloughing of the epithelial cells, o Blebbing in the early stages o Calcifications or mitotic figures
Figure 1. Pathophysiology of Ischemia and Tubule Cell Injury.
C. Toxic Acute Tubular Necrosis
Affects the proximal convoluted tubules (because this is where most reabsorption takes place)
May be non-specific
Some agents have distinct findings (however we usually don’t see this)such as: o Mercuric chloride – large acidophilic inclusions,
necrotic, desquamated or calcified o Carbon tetrachloride – neutral lipids in injured cells o Ethylene glycol –marked ballooning and hydropic or
vacuolar degeneration o Calcium oxalate crystals in lumen
Appear the same as ischemic necrosis, so differentiate clinically
D. Clinical Course of Acute Tubular Necrosis
Figure 2. Acute tubular necrosis (L: Tubule with no brush
border cells, sloughing of the epithelial cells, flattened cuboidal cells and widened lumen, with cell debris in the lumen [circle]; R:
Associated with some interstitial infiltrates (circle) but most prominent is tubular damage (rectangle), calcification of cells
(arrow) *note calcification is from the death of cells Dystrophic
calcification CLINICAL COURSE
Highly variable
Treatment is supportive e.g. hydration and removal of cause (important to know causative agent to know the treatment)
PHASES
Initiation Phase o Lasts for 36 hours o Inciting event o This phase is dominated by this event o E.g. surgery/obstetric shock o Decline in urine output with increase BUN o Oliguria Due to transient decrease in blood flow to
kidneys
Maintenance phase o Sustained decrease in urine output to between 40-400
ml/day (oliguria) o Salt and water overload due to abnormality of the
patients hemodynamics o Rising BUN, hyperkalemia, metabolic acidosis o Dialysis patient may need temporary dialysis until
the kidney can recover
TOPIC OUTLINE
I. Acute Tubular Necrosis
A. Causes of Acute Tubular Necrosis B. Ischemic Acute Tubular Necrosis C. Toxic Acute Tubular Necrosis D. Clinical Course of Acute Tubular Necrosis
II. Tubulointerstitial Nephritis III. Pyelonephritis and Urinary Tract Infection
A. Acute Pyelonephritis B. Polyomavirus (BK Virus Nephropathy)
IV. Chronic Pyelonephritis V. Xanthogranulomatous Pyelonephritis VI. Drug-Induced Tubulointerstitial Nephritis VII. Acute Drug-Induced Interstitial Nephritis VIII. Analgesic Abuse Nephropathy IX. Nephropathy Associated with NSAIDS X. Chinese Herbs Nephropathy XI. Urate Nephropathy XII. Multiple Myeloma XIII. Vascular Diseases
A. Benign Nephrosclerosis B. Malignant Nephrosclerosis C. Renal Artery Stenosis
Mina, Mina, Miral Page 2 of 5
Lec 08: Pathology of Tubular Diseases OS214
Recovery phase o Steady rise in urine volume (up to 3L per day) o Tubules still damaged (urine spillage of water Na and
K) o Clue when you see glucosuria in non-diabetic patients o Hypokalemia Clinical problem o Vulnerable to infections o Recovery is variable
Nephrosis may return to normal after several months since it is an acute case
Some cases have a repeat biopsy done and results show similar clinical findings
o Treatment: removal of offending agent and supportive therapy
Prognosis o Depends on the underlying cause o Toxic (removal of offending agent) vs. Ischemic
(address the underlying cause)
Shock related to sepsis, extensive burns or other causes of mult-organ failure >50% mortality
II. TUBULO-INTERSTITIAL NEPHRITIS (TIN)
Involves the renal parenchyma
Etiology of Primary Tubulointerstitial Nephritis o Infections
Acute bacterial pyelonephritis Chronic pyelonephritis (including reflux
nephropathy) Other infections (e.g. Viruses, parasites)
o Toxins Drugs Acute hypersensitivity interstitial nephritis Analgesic nephritis Heavy metals Lead, Cadmium
o Metabolic Diseases Uratenepropathy Nephrocalcinosis (hypercalcemic nephropathy) Hypokalemic nephropathy Oxalate nephropathy
o Physical factors Chronic urinary tract obstruction Radiaton nephritis
o Neoplasms Multiple myeloma
o Immunologic Reactions Transplant rejection Sjögren syndrome
o Vascular Diseases o Miscellaneous
Balkan nephropathy Nephronophthisis – medullary cystic disease
complex Other rare causes (sarcoidosis) “idiopathic” interstitial nephritis
Etiology of Secondary Tubulointerstitial Nephritis o Secondary to a glomerular disease (e.g. Crescentic
Glomerulonephritis very active glomerulus very active tubules lots of inflammatory cells)
May be acute or chronic
Must be differentiated from glomerular diseases o Look at the glomeruli. If there are
abnormalities/infiltrates that are out of proportion (too much infiltrates despite a normal looking glomeruli), think of possible Primary Acute Tubulointerstitial Nephritis
o If there are overactive glomeruli, think of Secondary Acute Tubulointerstitial Nephritis
Infection is usually ascending o Bacteria from the urethra adheres to the mucosa, going
up the bladder. Abnormality in vesicoureteral valve causes it to enter the ureter and eventually the kidney.
o From Ma’am: We do not like it when it reaches the kidney. This is because there is permanent damage once it the infection resolves.
III. PYELONEPHRITIS AND URINARY TRACT INFECTION
Ascending Infection o Most common, more common than hematogenous o Colonization of the distal urethra and introitus by
coliform bacteria o From the urethra to the bladder o Multiplication in the bladder o Vesicoureteral reflux (incompetence of vesicoureteral
valve) o Intrarenal reflux
Figure 3. Ascending vs Hematogenous Infection
Most common cause is ascending through the urinary tract.
A. Acute Pyelonepthritis
Involves the renal pelvis (pyelo = pelvis) o Cannot be reached by renal biopsy because it’s too
deep; thus, diagnosis is usually limited to acute tubuloinsterstital nephritis
o However, if perform nephrectomy (surgical removal of the kidneys), and we see inflammation of the renal pelvis aside from the parenchyma, then we consider it as acute pyrlonephritis
Acute suppurative inflammation caused by bacterial infection
Complications o Papillary Necrosis – usually seen in diabetics o Pyonephrosis – purulent material in renal pelvis
(pyo=pus) o Perinephric abscess – infection extends outside the
kidneys, infecting surrounding fat and adjacent structures.
Prompt diagnosis and treatment is required among suspected patients to avoid nephrectomy. o This could be detected by urinalysis and urine culture
Predisposing conditions o Urinary obstruction o Instrumentation of urinary tract - catheterization o Vesicoureteral reflux (VUR) o Pregnancy o Patinet’s sex and age – older patients, usually females o Preexisting renal lesions o Diabetes Mellitus o Immunosuppression and immunodeficiency
Kidneys are larger than normal due to the infection
Figure 4.Acute Pyelonephritis. Microabscessces (circled) – pinpoint finely granular surface, neutrophils (dark spots,
upper right image), Leukocyte casts (arrow) From Ma’am: You can suggest acute pyelonephritis just by looking at a renal biopsy of a small cortical sample if you
see leukocyte casts within tubules.
Mina, Mina, Miral Page 3 of 5
Lec 08: Pathology of Tubular Diseases OS214
Manifestations o Pain at the costovertebral angle (kidney punch sign) o Fever and malaise o Dysuria, frequency, and urgency o Pyuria, leukocyte casts o Urine culture o E. coli and polyoma virus (common in transplant
patients, viral titers for this are done)
B. POLYOMAVIRUS (BK VIRUS NEPHROPATHY)
Most common viral infection in kidney transplant patients
Three variants o BK – common cause of infection o SV (Simian virus) & JC – rarely causes infection
BK – initials of Sudanese patient who first diagnosed with the virus
Came about due to the more aggressive immunosuppressive drugs given to transplant patients
Diagnosis o Urine decoy cell determination o Freshly voided urine + special fixative observe the
nuclei of the cells from urine Positive result: nuclear clearing with chromatin pushed to the sides
o A positive urine decoy cell determination test indicates infection anywhere along the urinary tract
o Positive result is indication for graft biopsy (graft – transplanted organs)
If graft biopsy indicates infection, treatment is by lowering immunosuppressive drugs and anti-viral agents
Figure 5. Polyomavirus (BK virus) nephropathy. Urine
decoy cells (left) – screening test, and graft biopsy with infected cells (right). Note the nuclear clearing, ground
glass appearance and chromatin pushed to the periphery (circle).
Diagnosis: 5 decoy cells per HPF, or 10 decoy cells per LPF.
Then do kidney biopsy to confirm.
Infects only tubular and parietal epithelial cells o This is because parietal cells are connected to the
proximal convoluted tubule (PCT)
Figure 6.Polyoma virus infection imaging. (clockwise, from
top left) 1. immunostaining with SV-40, infected epithelial cells - Take note of the nuclei, not the cytoplasm. 2.
Infected cells (circled) with chromatin pushed to the side, and inclusion (virus) present. 3. Viral particles seen in a
paracrystalline array. You can see more cells in an SV-40 stain.
IV. CHRONIC PYELONEPHRITIS
Chronic tubulointerstitial inflammation and renal scarring associated with pathologic involvement of the calyces and pelvis
Hallmark
Coarse, discrete, corticomedullary scar overlying a dilated, blunted, or deformed calyx
Two forms o Reflux nephropathy – child with recurrent infection!
More common Occurs in early childhood as a result of infection
on congenital vesicoureteral and intrareal reflux o Chronic obstructive pyelonephritis
Grossly appears as coarsely granular cortical surface with irregularity o Vs. acute pyelonephritis which presents with pinpoint
microabscesses o Irregularities of the surfaces are due to the scars
Figure 6.Chronic Pyelonephritis (gross). Note the coarsely granular and irregular cortical surface.
Figure 7.Chronic Pyelonephritis (microscopic).Features similar to end stage renal disease; however, there is involvement of the renal pelvis.
Note the ff: interstitial infiltrates, sclerosis (circle), and colloid casts/thryoidization (arrow)
V. XANTHOGRANULOMATOUS PYELONEPHRITIS
Unusual and rare
Associated with Proteus infection and obstruction
Yellow orange nodules
Differential diagnosis with Renal Cell CA (similar foamy macrophages) o Sometimes, frozen section may lead to misdiagnosis
because these appear as clear cells, wherein macrophages can resemble RCCA
Figure 8.Xanthogranulomatous Pyelonephritis. Note the yellow orange nodules (arrow) on gross specimen and
foamy macrophages (circle) on microscopic specimen, you can see bubbly cytoplasm but not the fibrous septate(?)
that lines RCCA
VI. DRUG-INDUCED TUBULOINTERSTITIAL
Produce renal in 3 ways o They may trigger an interstitial immunologic reaction
(acute hypersensitivity reaction) o They may cause Acute Renal Failure o They may cause subtle but cumulative injury (CRI) –
more chronic
VII. ACUTE DRUG-INDUCED INTERSTITIAL NEPHRITIS
Penicillins (methicillins, ampicillins), synthetic antibiotics (rifampicin), diuretics (thiazides), NSAIDS (phenylbutazones) and miscellaneous drugs (cimetidine)
Withdrawal of drug leads to full recovery
Mina, Mina, Miral Page 4 of 5
Lec 08: Pathology of Tubular Diseases OS214
Disease begins at about 15 days (2-40 days) after exposure to the drug
Patients may present with fever, eosinophilia (may be transient),rash (25%) and renal abnormailities
Hematuria, mild proteinuria, and leukocyturia
A rising serum creatinine level or acute renal failure with oliguria develop in 50%
One needs to review medications to determine which one causes the injury
Figure 9.Acute Drug-Induced Interstitial Nephritis.Note
eosinophils (Ma’am says it is a bonus, because sometimes you cannot see this). Make sure however that DIIN is still
part of your Ddx.
VIII. ANALGESIC ABUSE NEPHROPATHY
A form of chronic renal disease caused by excessive intake of analgesic mixtures and characterized morphologically by CTIN
Complications
Transitional Cell CA (TCCA) of renal pelvis
Large quantities of mixtures of at least 2 antipyretic analgesics
Aspirin, caffeine and acetaminophen (a metabolite of phenacetin)
Papillary Necrosis o Sloughing off of papillae o Not only seen in analgesic nephropathy, but also in
other diseases (see Figure 10). o Mixture of aspirin and phenacetin o Combined with water depletion
Papillary Necrosis occurs first
Cortical tubulointerstitial nephritis is a secondary phenomenon
Figure 10. Papillary Necrosis and other Associated
Diseases. Note that in analgesic nephropathy, almost all papillae are affected.
Acetaminophen injures cells by both covalent binding and oxidative damage
Aspirin induces its effect by inhibiting the vasodilatory effects of prostaglandin, predisposing the papillae to ischemia
Injury due to a combination of direct toxic effects and ischemia
Prone to development of transitional cell CA of the renal cell pelvis
Figure 11.Papillary Necrosis (Gross and
MIcroscopic).Gross finding shows necrotic material form papillae, filling the calyces. Microscopic features show
necrotic material.
More common in women, psychoneurotic patients and factory workers due to recurrent headaches and muscle pains
Headache, anemia, and gastrointestinal symptoms accompany analgesic nephropathy
X. CHINESE HERBS NEPHROPATHY
Aristolochic acid – component associated with nephropathy
Increased incidence of carcinoma in the kidney and urinary tract
For those who are fond of drinking chinese herbs and other supplements – be careful!
Sometimes very subtle, and persists for several months, and biopsy reveals chronic changes only then the clinician elicited in the history the intake of chinese herbs
XI. URATE NEPHROPATHY
Three types o Acute uric acid nephropathy
Caused by precipitation of uric acid crystals in the renal tubules leading to obstruction of nephrons and development of acute renal failure
Leukemias and lymphomas who are undergoing chemotherapy
Drugs increase the death of tumor cells and uric acid is released as the nuclei of these cells disintegrate
o Chronic urate or gouty nephropathy More protracted form of hyperuricemia Deposition of nonsodiumurate crystals Birefringent needle-like crystals in the tubules or
interstitium Tophus – consists of foreign body giant cells,
mononuclear cells and a fibrotic reaction Subtle disease, slowly progressive
o Nephrolithasis – large stones Uric acid stones present in 22% of patients with
gout Uric acid stones present in 42% of patients with
secondary hyperuricemia Very big stones
Figure 12.Urate Nephropathy.Note white streaks in gross
(circles) which are crystals, and needle-like pattern in microscopic finding (spaces once occupied by crystals, which dissolves during slide preparation) surrounded by
inflammatory cells
Mina, Mina, Miral Page 5 of 5
Lec 08: Pathology of Tubular Diseases OS214
XII. MULTIPLE MYELOMA
Renal involvement by multiple myeloma is sometimes an ominous manifestation
Renal damage is brought about by: o Bence-Jones proteinuria and cast nephropathy
Bence-Jones tubular casts appear as pink to blue amorphous masses, sometimes concentrically laminated, surrounded by multinucleated giant cells
Some light chains are directly toxic to epithelial cells
Bence-Jones proteins combine with Tamm-Horsfall protein to form casts that obstruct tubules and produce an inflammatory reaction.
o Amyloidosis Accumulation of light chains with predisposition to
form amyloid fibrils (6-24% of myeloma patients) o Light chain deposition disease
Deposited in the glomerular basement membrane and mesangium and tubular basement membrane
o Hypercalcemia and hyperuricemia
Acute renal failure or chronic renal failure
Seen in older patients, has poor prognosis (few months-few years)
Figure 13.Multiple Myeloma.Note the casts inside the tubules. Casts
are laminated, resembling annular rings in a tree or appear fractured.
XIII. VASCULAR DISEASES
A. Benign Nephrosclerosis
Kidney associated with sclerosis of renal areterioles and small arteries
Two processes o Medial and intimal thickening
Response to hemodynamic changes, aging, genetic defects or a combination
o Hyaline deposition in arterioles Caused partly by extravasation of plasma proteins
through injured endothelium and partly by increased deposition of basement membrane matrix
Figure 14. Hyaline Deposition in Arterioles seen in Benign Nephrosclerosis
B. Malignant Nephrosclerosis
Renal disease associated with accelerated or malignant phase of hypertension
Flea-bitten kidney
Fibrinoid necrosis of arterioles
Hyperplastic arteriolitis --- onion skinning
Diastolic BP of >130 mmHg
Papilledema retinopathy
Encephalopathy
Cardiovascular abnormalities
Renal failure
Hypertensive crises o Loss of consciousness and convulsions
Figure 15. a. Fibrinoid necrosis. RBCs may be seen within the
vascular wall. b. Hyperplastic arteriolitis – onion skinning
C. Renal Artery Stenosis
Unilateral --- uncommon cause of HPN
Most common cause is occlusion by atheromatous plaque at the origin of the renal artery
Fibromuscular dysplasia --- fibrous or fibromuscular thickening of intima, media or adventitia
Figure 16. a. fibromuscular dysplasia; can be intimal, medial or
adventitial. b. atheromatous plaque with the presence of cholesterol clefts.
One Eight, Dominate!
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