Weird body fluids

Occasionally, something comes up in the CICM exam that can only be described as "guess what gross stuff that is". This can take many different shapes:

• Red urine, in Question 16.2 from the first paper of 2023
• Chyle, in Question 10.2 from the second paper of 2013
• Supernatant fat in Question 7.1  from the first paper of 2010

It is the authors firmly held opinion that all examiners have rich stores of photographs from their practice where weirdly coloured body fluids are documented, and trainees should prepare themselves for the appearance of these horrors in the written paper.

"Chicken fat supernatant" in hyperlipidaemia

Question 7.1  from the first paper of 2010 flaunted some blood tubes before the candidates; the specific feature was the presence of "chicken fat supernatant" suggestive of gross hyperlipidaemia. Other features associated with this condition may be lipaemia retinalis, corneal arcus senilis and xanthelasma of the skin or tendons.

The pictures were of a fairly poor quality. However, one must be grateful - most of the time these days the college remove the pictures from their papers.

The specific "chicken fat" supernatant demonstrated in the college photograph is characteristic - that "cream" is all chylomicrons. In fact, this finding had in the olden days formed part of the classification of hyperlipidaemias- they used to observe "standing serum" to see if a supernatant would form. In the most severe forms of hyperlipidaemia, this fatty impurity can cause the blood to look milky and turbid.

In case anybody ever wanted to see a better picture of the supernatant, here is a shot of my collague's hand holding an EDTA tube with the blood of a pancreatitis patient. The presenting triglyceride level was 45g/L.

Causes of such appearance of the blood are all answers to the question, "What causes, or is associated with, insanely high serum lipid levels?" As far as recent literature for this obscure topic, one cannot go past the 1994 article by NJ Stone who listed a series of causes in his abstract. Mixed with the college answer, 

Associations:

• Severe pancreatitis
• Hypothyroidism (classically associated with severe hyperlipidaemia)
• Anorexia nervosa

Causes:

• Corticosteroids
• Cyclosporine
• Oestrogens
• Thiazides
• Alcohol (in excess)

• Familial hyperlipidaemia
• TPN use (especially if you take the blood from the same CVC lumen, like some kind of idiot)
• Propofol infusion
• Thoracic duct injury

The latter comes from an answer to Question 7.1  from the first paper of 2010, written by my esteemed colleague Dr Hatem Elkady during one of our practice exam papers.  He is proven correct  by a 1973 paper (Cremer et al). The authors acquired a bunch of rats, ligated their thoracic ducts,  then watched their serum lipids go through the roof. The liver, which logically becomes congested with chylomycrons, undergoes  "pronounced morphological alterations". Needless to say, full marks were awarded. It raises the question of whether or not an inventive "outside the box" answer would score anything in the real college exam if the demonstration of its correctness requires a thirty-second Google search.

Causes or red urine 

Question 16.2 from the first paper of 2023 gave us red urine in a patient pulled out of an exploded chemical warehouse, suggesting that cyanide toxicity leading to hydroxocobalamin use and various forms of blast trauma would need to be at the top of the list of differentials:

• Haematuria:
  • The patient may have had an injury to the kidneys or the renal tract (for example, as the result of being thrown by the blast)
  • This is revealed by finding red cells in the urine microscopy
• Haemoglobinuria:
  • The patient may have developed haemolysis as the result of severe thermal damage or blast injury
  • The presence of free haemoglobin in the blood, or a dipstick positive for blood in the absence of any red cells on urine microscopy, would be diagnostic
• Myoglobinuria:​​​​​​​
  • Blast injury can present with rhabdomyolysis due to widespread muscle damage
  • The resulting myoglobinuria can be detected by a urinary myoglobin level, and would also yield a a dipstick positive for blood in the absence of any red cells on urine microscopy (because the dipstick tests for haem, and myoglobin contains haem)
• Hydroxocobalamin:
  • "​​​​​​​Explosion in a chemical factory" is the college's way of making the trainees think about cyanide toxicity, which calls for a large dose of hydroxocobalamin. 
  • If for whatever reason this was not self-evident from the medication chart, one may be able to confirm the presence of a red non-haem dye in the urine by testing it for blood with a urine dipstick, which would of course be negative.

Other exciting possibilities where the explosion is irrelevant include:

• Not haematuria, but blood in urine:
  • Menstruation
  • Genital injury
• Other causes of intravascular haemolysis:
  • A mechanical valve
  • ECMO
  • G6PD deficiency
  • Sickle cell anaemia
  • Transfusion reaction
• Drugs:
  • Rifampicin, which, to be fair, is more orange
  • Isoniazid
  • Warfarin
  • Riboflavin
• Errors of metabolism
  • Porphyria
• Beetroot consumption, which causes harmless "beeturia"