WBR0970
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biochemistry |
| Sub Category | SubCategory::General Principles |
| Prompt | [[Prompt::A 45-year-old man with previous history of hepatitis C infection complains of progressively increasing fatigue, loss of appetite and bleeding tendency. Physical exam reveals yellowing of the sclera and the skin in addition to an increase in the abdominal girth. During physical exam, the patient is asked to push his hands down on the midline of the abdomen, the examiner then taps one flank, while feeling on the other flank for the tap. The examiner is able to feel the tap on the other side. A set of laboratory tests is ordered. What are the expected changes in the BUN and ammonia blood levels respectively?]] |
| Answer A | AnswerA::Decreased, decreased |
| Answer A Explanation | [[AnswerAExp::In cirrhosis, hepatocytes are affected; therefore, urea cycle is not as functional as it is in a normal liver. Ammonia is not converted to urea leading to an elevated blood level of ammonia and a decreased level of blood urea nitrogen (BUN) level.]] |
| Answer B | AnswerB::Decreased, increased |
| Answer B Explanation | [[AnswerBExp::This answer is incorrect because in cirrhosis the blood level of ammonia is elevated the blood urea nitrogen (BUN) level is decreased.]] |
| Answer C | AnswerC::Increased, unchanged |
| Answer C Explanation | [[AnswerCExp::This answer is incorrect because in cirrhosis the blood level of ammonia is elevated the blood urea nitrogen (BUN) level is decreased.]] |
| Answer D | AnswerD::Increased, increased |
| Answer D Explanation | [[AnswerDExp::This answer is incorrect because in cirrhosis the blood level of ammonia is elevated the blood urea nitrogen (BUN) level is decreased.]] |
| Answer E | AnswerE::Unchanged, increased |
| Answer E Explanation | [[AnswerEExp::This answer is incorrect because in cirrhosis the blood level of ammonia is elevated the blood urea nitrogen (BUN) level is decreased.]] |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::The patient complains of fatigue, loss of appetite and bleeding tendency in the context of hepatitis C infection. Moreover, the exam reveals jaundice and ascites as demonstrated by the fluid wave test. The fluid wave test s performed by having the patient push their hands down on the midline of the abdomen, then the examiner taps one flank, while feeling on the other flank for the tap. Fluid allows the tap to be felt on the other side. The patient's signs and symptoms are most likely due to liver cirrhosis secondary to chronic hepatitis C.
Ammonia is converted in the liver to urea by a set of mitochondrial and cytoplasmic enzymes in the hepatocytes. In cirrhosis, hepatocytes are affected; therefore, urea cycle is not as functional as it is in a normal liver. Ammonia is not converted to urea leading to an elevated blood level of ammonia and a decreased level of blood urea nitrogen (BUN) level. Educational objective:
Ammonia is converted in the liver to urea by a set of mitochondrial and cytoplasmic enzymes in the hepatocytes. In cirrhosis, the urea cycle is affected leading to an elevated blood level of ammonia and a decreased level of blood urea level. |
| Approved | Approved::No |
| Keyword | WBRKeyword::Urea, WBRKeyword::ammonia, WBRKeyword::Cirrhosis |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |