Tubular diseases: Presentations, Etiologies and Complications

Question 1

What are the causes of postrenal azotemia?

Answer 1

• Prostate hypertrophy or cancer
• Stone in the ureter
• Cervical cancer
• Urethral stricture
• Neurogenic (atonic) bladder
• Retroperitoneal fibrosis (from bleomycin, methylsergide or radiation)

Question 2

What are the causes of intrinsic renal disease?

Answer 2

• ATN from toxins (contrast agents, aminoglycosides, cisplatin, amphotericin, cyclosporine, and NSAIDs)or prolonged ischemia
• Acute (allergic) interstitial nephritis (commonly from meds e.g. penicillin)
• Rhabdomyolysis and hemoglobinuria
• Crystals from hyperuricemia, hypercalcemia, or hyperoxaluria
• Proteins e.g. Bence-Jones proteins in multiple myeloma
• Poststreptococcal infection

Question 3

What is the presentation of acute kidney injury (AKI)?

Answer 3

May be only an asymptomatic rise in BUN and Cr.

When symptomatic, the pt presents with:

• Nausea and vomiting
• Fatigue/malaise
• Weakness
• SOB

Question 4

What are the features of severe AKI?

Answer 4

• Confusion
• Arrhythmia from hyperkalemia and acidosis
• Sharp, pleuritic chest pain from pericarditis

Question 5

What is the typical presentation of postrenal azotemia?

Answer 5

Enlargement/distention of the bladder and massive diuresis after placement of a Foley catheter. Hydronephrosis may be seen unilaterally or bilaterally on sonogram.

Question 6

Describe the onset of AKI with the following toxins:

• Contrast media
• Vancomycin, gentamicin, amphotericin, cisplatin
• Tumor lysis syndrome

Answer 6

• Contrast media: very rapid onset injury, with Cr rising the next day
• Vancomycin, gentamicin, amphotericin, cisplatin, acyclovir: slower onset injury of 5-10 days
• Tumor lysis syndrome (hyperuricemia): onset of 2 days following start of chemotherapy

Question 7

What are the causes of rhabdomyolysis?

Answer 7

• Trauma
• Snake bite
• Prolonged immobility
• Seizures
• Crush injuries

Question 8

In ATN, what increases the risk of aminoglycoside or cisplatin toxicity?

Answer 8

Low magnesium level

Question 9

How does AKI from ethylene glycol present?

Answer 9

Pt who ingested an unknown substance presents with renal failure 3 days later along with a low calcium level and abnormal UA.

The calcium is low because it was used to form the envelope-shaped oxalate crystals that caused the AKI.

Question 10

How does the risk of ATN relate to the age of the pt?

Answer 10

The risk of ATN is directly proportional to age. This is because we lose 1% of our renal function for every year past age 40.

Question 11

What is hepatorenal syndrome? How does it present? With which type of AKI does it share lab values?

Answer 11

HR syndrome is renal failure that results secondary to liver disease. The kidneys are intrinsically normal. Look for:

• Severe liver disease (cirrhosis)
• New-onset renal failure with no other explanation
• Very low urine sodium 20:1

HR syndrome shares lab values with prerenal azotemia.

Question 12

How do atheroemboli cause AKI? What is the presentation?

Answer 12

Cholesterol plaques may be broken off the aorta or coronary arteries during catheter procedures and the emboli can get lodged in the kidneys, leading to AKI.

Along with signs and Sx of AKI, the pt will present with:

• Blue/purplish skin lesions in fingers and toes
• Livedo reticularis
• Ocular lesions

Question 13

What is acute (allergic) interstitial nephritis? What are the causes of it?

Answer 13

AIN is a form of AKI in which antibodies and eosinophils attack the cells lining the tubules as a reaction to drugs (70%), infection, and autoimmune disorders (SLE, Sjögren syndrome, sarcoidosis).

The most common medications that cause AIN are:

• Penicillins and cephalosporins
• Sulfa drugs
• Phenytoin
• Rifampin
• Quinolones
• Allopurinol
• PPIs

Question 14

The drugs that cause AIN are penicillins, cephalosporins, sulfa drugs, phenytoin, rifampin, quinolones, allopurinol, and PPIs. What else do all of these drugs have in common?

Answer 14

The drugs that cause AIN also cause:

• Drug allergy and rash
• Stevens-Johnson syndrome
• Toxic epidermal necrolysis (TEN)
• Hemolysis

*They all can damage the skin, kidneys, and RBCs

Question 15

What is the presentation of AIN?

Answer 15

Look for AKI (elevated BUN and Cr) with:

• Fever (80%)
• Rash (50%)
• Arthralgias
• Eosinophilia and eosinophiluria (80%)

*AIN from NSAIDs does NOT present with eosinophiluria

Question 16

What is the presentation of analgesic nephropathy?

Answer 16

• ATN from direct toxicity to the tubules
• AIN
• Membranous glomerulonephritis
• Vascular insufficiency of the kidney from inhibiting prostaglandins
• Papillary necrosis

Question 17

What is papillary necrosis? What are the causes?

Answer 17

Papillary necrosis is sloughing off of the renal papillae. It is caused by:

• Toxins e.g. NSAIDs
• Sudden vascular insufficiency

PN does not happen to healthy pts. Look for extra NSAID use with a history of:

• Sickle cell disease
• Diabetes
• Urinary obstruction
• Chronic pyelonephritis

Question 18

What is the pres. of papillary necrosis?

Answer 18

Sudden onset of flank pain, fever, and hematuria in a pt with one of the diseases previously listed.

*It may be very hard to distinguish PN from pyelonephritis

Question 19

Summary of tubular disease

Answer 19

• Generally, they are acute
• Tubular diseases are caused by toxins, infections and autoimmune diseases
• NONE of them EVER cause nephrotic syndrome or give massive proteinuria
• Biopsy is NOT needed to establish diagnosis
• They are NOT treated with steroids
• They are NOT treated with immunosuppressive drugs
• The underlying cause is treated (correcting hypoperfusion and removing the toxins)

Question 20

What are the causes of prerenal azotemia?

Answer 20

• Hypotension: sepsis, anaphylaxis, bleeding or dehydration
• Hypovolemia: diuretics, burns, pancreatitis
• Renal artery stenosis
• Relative hypovolemia: CHF, constrictive pericarditis, tamponade
• Hypoalbuminemia
• Cirrhosis
• NSAIDs (constrict the afferent arteriole)
• ACEIs (dilate the efferent arteriole)