Tubulointerstitial Disorders

Question 1

Fanconi’s Syndrome

Answer 1

Proximal tubule dysfunction
Include RTA type II (proximal tubule)
Inherited or Acquired
- Acquired = *multiple myeloma, also ifosfamide, amyloidosis, heavy metals, PNH

Causes loss of (presence in urine of…)

• bicarb
• glucose
• phosphate
• amino acids
• uric acid
• proteins

Non-AG metabolic acidosis (due to bicarb loss) + hypokalemia
Failure to thrive, malnutrition, volume depletion

Question 2

Fanconi’s Syndrome

Answer 2

Proximal tubule dysfunction
Include RTA type II (proximal tubule)
Inherited or Acquired
- Acquired = *multiple myeloma, also ifosfamide, amyloidosis, heavy metals, PNH

Causes loss of (presence in urine of…)

• bicarb
• glucose
• phosphate
• amino acids
• uric acid
• proteins

Non-AG metabolic acidosis (due to bicarb loss) + hypokalemia
Failure to thrive, malnutrition, volume depletion

Question 3

Autosomal Dominant Polycystic Kidney Disease

Answer 3

• Genetic disease
• PKD1 (more severe), PKD2
• Bilateral renal cysts
• Nephromegaly (big kidneys)
• Cysts grow and compress blood vessels and decrease flow –> RAAS activation –> HTN
• Flank pain
• Hematuria
• Renal insufficiency and failure
• Extrarenal cysts (Hepatic, Pancreatic, Ovarian, Testicular)
• Colon diverticula
• Aneurysms

RFs = younger age at diagnosis, black, male, hematuria, HTN. increase kidney size, PKD1

Treat: control HTN, protein restriction, cyst drainage

Question 4

Acute Tubular Necrosis

Answer 4

One of the most common cause of acute renal failure

• Ischemic or nephrotoxic insult to tubular epithelial cells –> necrosis
• MUDDY BROWN CASTS in urine due to dead epithelial cells in tubule
• Low GFR
• More urea and creatinine in blood (due to not getting filtered out - low GFR)
• Looks similar to Prerenal Azotemia

Question 5

Allergic (Acute) Interstitial Nephritis

Answer 5

Inflammation of interstitium
Often caused by drug therapy reaction
- NSAIDS, Penicillins, Rifampin, Sulfa Diuretics
Infiltration of immune cells

Other causes: Diabetes, SCD, Pyelonephritis, infections (strep

• Oliguria
• Eosinophiluria
• Fever
• Rash
• Renal Papillary Necrosis

Question 6

Medullary Sponge Kidney

Answer 6

Cysts are in medulla
Dilated and malformed collecting ducts

Often asymptomatic or…

• Hematuria
• UTIs (due to stagnent urine cause of cysts/stones)
• Kidney Stones (nephrolithiasis)

Diagnosed via IV pyelogram
Appearance of BRUSH or feather radiating toward calyx

Question 7

Sickle Cell Nephropathy

Answer 7

Renal involvement in SCD

• Typically concentrating defect
• Hematuria common
• Papillary necrosis and renal infarction possible
• Hyperkalemia due to impaired K secretion in collecting tubule
• Proteinuria possible –> progressive renal dysfunction

Question 8

Multiple Myeloma

Answer 8

Excess monoclonal Igs due to neoplastic proliferation
Men
65+
Hypercalcemia and renal failure possible

• Light chain toxicity in kidneys causes renal insufficiency
• Cast nephropathy (aka MYELOMA CAST) when light chains bind to Tamm-Horsefall Mucoprotein

Question 9

Granulomatosis with Polyangiitis (Wegener’s Granulomatosis)

Answer 9

Small vessel vasculitis

• 90% cANCA positive

Affects... 
Nasopharynx
- persistant rhinorrhea
- bloody nasal discharge
- oral/nasal ulcers
- sinus pain
Lungs
- breathing difficult

• • Kidneys
• inflammation restricts blood flow to glomeruli –> Acute Glomerulonephritis
• hematuria, proteinuria, RBC casts

Question 10

Lead poisoning

Answer 10

Basophilic stippling on peripheral smear

Abdominal colic, extensor muscle weakness, encephalopathy, memory impairment, HTN

Increased urinary lead excretion

Acute Lead Nephropathy –> Fanconi’s Syndrome

• Losing a lot of ions/ proteins/ glucose
• Proximal tubule defect
• Seen in children with lead encephalopathy
• Chelation may reverse

Chronic Lead Nephropathy

• Progressive tubulointerstitial nephritis from prolonged lead exposure
• tubular atrophy, fibrosis
• chelation not helpful

Question 11

Bartter Syndrome

Answer 11

Autosomal recessive

Affects NaCl reabsorption in ascending limb

• Impairs Na, Cl reabsorption
• Salt and water loss

Increase RAAS
Increase aldosterone –> K+ and H+ excretion –>
- hypokalemia
- metabolic alkalosis

Decreased calcium reabsorption –>

• hypercalciuria,
• hypocalcemia
• renal stones (nephrolithiasis)

Acts like a loop diuretic (so also blunted response)

Question 12

Gitelman Syndrome

Answer 12

Autosomal recessive

Impairs distal convoluted tubule NaCl cotransporter function

Seen in late childhood - adulthood

Salt and water loss –> volume depletion + activation of RAAS

• Severe hypomagnesemia
• hypercalcemia
• Metabolic alkalosis
• hypokalemia
• Normotension

Acts like a thiazide diuretic (so also blunted response)

Question 13

Liddle Syndrome

Answer 13

Autosomal dominant

Increased function epithelial Na channel in collecting tubule

• Seen in childhood mostly
• Increased salt and water reabsorption –> volume overload
• hypokalemia
• metabolic alkylosis
• hypertension

Acts like mineralocorticoid excess
Blunted response to thiazide diuretics