TUBULOINTERSTITIAL DISORDERS

Question 1

What is acute tubular necrosis? List 3 causes

Answer 1

sudden damage to tubular epithelial cells

• Ischaemia (any cause of severely reduced bloodflow)
• Drugs
• Toxins

Question 2

What happens to the afferent arterioles in ischaemia ATN?

Answer 2

Vasoconstriction causing a reduction in EGFR → worsens problem

Question 3

Which antibiotic is well known for causing ATN? List another drug commonly used in radiography also associated with the condition. Which endogenous pigment can also cause this?

Answer 3

Aminoglycosides

Contrast dye

Myoglobin

Question 4

Which parts of the nephron are affected by ischaemic injury versus toxic injury?

Answer 4

• Ischaemic: proximal tubule, thick ascending limb (both contain lots of sodium/potassium ATPases)
• Toxic: proximal tubule only

Question 5

What are the three phases of ATN?

Answer 5

1. Injury → decline in urine OP
2. Maintenance: Oliguria, urea + Cr rise, hyperkalaemia, metabolic acidosis, lasts weeks
3. Recovery, tubular re-epithelialization: polyuria, hypokalaemia

Question 6

A patient on NSAID with a mild increase in urea and creatinine and improvement of renal function upon cessation of drug likely had which condition?

Answer 6

Chronic interstitial nephritis

Question 7

A patient complaining of gross, painless haematuria with clumps of blood, normal renal function likely has which condition? What causes this? What is a potential complication in terms of urine flow?

Answer 7

Papillary necrosis: coagulative necrosis of renal papillae

• No intrinsic renal failure, no white blood cell casts in urine
• May obstruct urine flow and cause retention

Sickle cell most important cause

Question 8

What condition should you consider in the acute onset of severe renal failure associated with obstetric catastrophes such as abruption of the placenta?

Answer 8

Cortical necrosis

Usually the cause is a major, catastrophic disorder that decreases blood pressure

Question 9

A patient presenting with acute kidney injury, low-grade fever and a maculopapular rash 2 to 3 weeks after exposure to an antibiotic is likely to have which condition? What is the most important step in the management of this condition?

Answer 9

Acute interstitial nephritis

Removal of drug that could’ve caused condition. Corticosteroids can be used if presentation is severe

Typical agents include sulfa drugs, penicillins, cephalosporins, rifampicin, non-steroidal anti-inflammatory and proton pump inhibitors

Question 10

Granular (muddy brown) casts in the urine are pathopneumonic of which disorder?

Answer 10

Acute tubular necrosis