Jaundice

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Jaundice

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USMLE® Step 1 style questions USMLE

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A 6-day-old female is brought to the pediatrician by her parents for evaluation of jaundice. She was born at 36 weeks gestation to a 29-year-old, gravida 1 para 1, woman via an uncomplicated vaginal delivery. According to her parents, the patient has had difficulty latching to her mother’s breast. The patient has passed meconium and produces 3-4 wet diapers per day. In the office, she is fussy but consolable. Physical examination shows depressed anterior and posterior fontanelles. Scleral icterus and jaundice of the head and chest are observed. Cardiac, pulmonary, and abdominal exams are noncontributory. Which of the following best describes the pathophysiology of this patient’s condition?  

External References

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Hyperbilirubinemia

jaundice with p. 400

Jaundice p. 400

alcoholic cirrhosis and p. 399

biliary tract disease p. 402

cholangitis p. 375, 402

cirrhosis p. 396

Crigler-Najjar syndrome p. 724

as drug reaction p. 248

fructose intolerance p. 78

galactosemia p. 78

graft-versus-host disease p. 117

hepatitis B p. 180

hepatocellular carcinoma p. 399

hereditary hyperbilirubinemias p. 401

leptospirosis p. 145

newborn hemolytic disease p. 414

painless p. 723

pancreatic cancer p. 402

ToRCHeS infections p. 181

transfusion reaction p. 112

yellow fever p. 165

Neonates

jaundice in p. 400

Obstructive jaundice p. 405

Phototherapy for jaundice p. 400

Transcript

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Content Reviewers

Jaundice, which doesn’t have the most intuitive name, comes from the french jaunice, meaning yellowing.

It’s also sometimes referred to as icterus though, the origin of which is even less intuitive, coming from the thought that jaundice could once be cured by looking at a yellow bird, the more you know!

Anyways, as you’ve probably gathered, jaundice involves someone taking on yellow pigments, specifically in the skin and eyes.

The yellowing pigment is caused by a compound called bilirubin, a component of bile and the main cause of bruises being yellow, and after its metabolism, the yellow-ness of urine and brown-ness of feces.

So since bilirubin’s our main culprit of yellow-ness, it’s super important to know where it comes from.

As red blood cells near the end of their lifespan—which is about 120 days—they’re eaten up or phagocytosed by macrophages in the reticuloendothelial system, aka the macrophage system, where the spleen plays the largest part, but it’s also made of parts of the lymph nodes.

K so first the macrophage eats up the blood cell, and hemoglobin is broken up into heme and globin, the globin is further broken into amino acids.

The heme on the other hand is split into iron and protoporphyrin, protoporphyrin is then converted into unconjugated bilirubin, or UCB.

Unconjugated bilirubin is the form of bilirubin that’s lipid-soluble, meaning it’s not water-soluble, sometimes it’s also known as indirect bilirubin.

Albumin in the blood then binds to UCB and gives it a lift over to the liver where it’s taken up by hepatocytes, where it’s conjugated by an enzyme called uridine glucuronyl transferase (UGT), making it now water soluble.

At this point the conjugated bilirubin is secreted out the bile canaliculi where it drains into the bile ducts and sent to the gallbladder for storage as bile.

Now when you eat a donut or something, your gallbladder secretes the bile and CB, it moves through the common bile duct to the duodenum of the small intestine and is converted to urobilinogen, or UBG, by intestinal microbes in the gut.

Now some of that urobilinogen is reduced to stercobilin which is excreted and responsible for the brown color of feces.

Sources

  1. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  2. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  3. "Yen & Jaffe's Reproductive Endocrinology" Saunders W.B. (2018)
  4. "Bates' Guide to Physical Examination and History Taking" LWW (2016)
  5. "Robbins Basic Pathology" Elsevier (2017)
  6. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  7. "A Systematic Approach to Patients with Jaundice" Seminars in Interventional Radiology (2016)
  8. "Unconjugated Hyperbilirubinemia and Early Childhood Caries in a Diverse Group of Neonates" American Journal of Perinatology (2009)
  9. "Jaundice in Older Children and Adolescents" Pediatrics In Review (2001)
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