Question 8.3

College answer

Syllabus topic/section:

2.1.11    Obstetric Intensive Care: Physiological changes related to pregnancy: L1

Discussion: 

Question 8.3 explicitly asked for 4 differential diagnosis and a rationale for each. Many candidates missed marks by not providing the rationale eg the clinical and laboratory features that support the diagnosis, or by suggesting a differential diagnosis not relevant to case.

Discussion

Systematically:

• Urea and creatinine are raised, suggesting renal failure
• Urea:creatinine ratio is basically normal (0.06)
• Albumin is low, which is consistent with normal pregnancy and critical illness
• The BSL is dramatically depressed, which suggests that the extent of the liver damage is greater than is revealed by the relatively mild LFT derangement
• The bilirubin is markedly increased, but the LDH is not, which suggests that haemolysis is not likely to be the main issue
• Urate is raised, which in obstetrics is a sinister marker of preeclampsia
• APTT and INR are increased, suggesting that, though the LFTs may be unimpressive, the liver function is poor
• Platelets are low, which is nonspecific and could mean either a sequestration, impaired production, or some consumptive process

So: this trope is Liver Failure in Pregnancy, and could be:

• Acute fatty liver of pregnancy could explain everything:
  • Usually presents exactly like this (vomiting, etc)
  • Bloods are also classical
  • It is not mandatory to have pre-exclampsia
  • Does not have to have renal failure, but often does
• A decompensation of chronic liver disease could explain everything
  • The LFTs are out of proportion to the coagulopathy and bilirubin rise because of the chronicity of the disease.
  • The confusion could be hepatic encephalopathy
  • Renal function could be pre-renal failure associated with the primary trigger for this decompensation, or it could be pre-renal syndrome
• Pre-eclampsia:
  • Suspected because of raised urate and renal failure
  • Usually, you would expect the blood pressure to be higher
  • Seizures are absent but the patient is confused
  • Does not have to have liver failure, but if it does:
• HELLP syndrome:
  • Platelets are down, LFTs are up, and there is enough urate to justify a diagnosis preeclampsia
  • However, the usual diagnostic criteria call for a raised LDH, which we do not have
  • The haemoglobin is not available, to look for haemolysis, but there is enough of an AST/ALT rise and bilirubin
  • The coagulopathy is not a part of the definition, but could be
  • But it could also be:
• Antiphospholipid syndrome
  • Because this is pregnancy and deteriorating during pregnancy is a well-worn trope of APLS. 
  • APTT and INR are elevated out of proportion to the LFT derangement, begging the question: is there some soluble anticoagulant?
• Acute liver failure of some non-pregnancy-related cause, that just so happens to have been found in a pregnant patient:
  • Viral hepatitis, for example, is much more common than acute fatty liver of pregnancy
  • would not be expected to create hypertension 
  • would be expected to have much higher LFTs
  • would not be associated with a raised urate (quite the opposite)