NBME 22 Absorption of nitrogenous products from the gastrointestinal tract (NBME Answers)

Retired NBME 22 Answers

nbme22/Block 3/Question#31 (reveal difficulty score)
A 35-year-old man is admitted to the hospital ...
Absorption of nitrogenous products from the gastrointestinal tract 🔍 / 📺 / 🌳 / 📖
tags:

+9 upvote downvote
submitted by ∗yotsubato(1208)

get full access to all content ⋅ pick a username

What do you use to treat Hepatic Encephalopathy? Lactulose. What does that do, it acidifies NH3 in the GI tract into NH4+ and promotes loss of the nitrogenous products that cause encephalopathy. This is how you remember this process.

get full access to all content ⋅ pick a username

carmustine FA 2019 pg 385 "Triggers --> increased NH3 production & absorption (due to GI bleed, constipation, infection)." +4

drzed To add, you can also use rifaximin which will act as a antibiotic decreasing the production of NH3 from gut flora. Same concept. +3

nevergoingtopost Lactulose is the correct treatment for hepatic encephalopathy, but it actually acidifies the GI tract (colonic metabolism of lactose → lactate). This favors the NH3 form and decreases NH4+. NH3 is then additionally pulled from the blood into the gut. +2

abhishek021196 @nevergoingtopost - lactulose actually increases NH4+ generation : Pg 401 FA 2021. +

+3 upvote downvote
submitted by dolphinpanda(3)

get full access to all content ⋅ pick a username

Increased bleeding in the GI tract also delivers hemoglobin and other proteins to the tract which are broken down to nitrogenous products and then absorbed

get full access to all content ⋅ pick a username

+0 upvote downvote
submitted by ∗dr.xx(176)

get full access to all content ⋅ pick a username

The most important waste product is ammonia (NH3). This small molecule crosses the blood–brain barrier and is absorbed and metabolised by the astrocytes, a population of cells in the brain that constitutes 30% of the cerebral cortex. Astrocytes use ammonia when synthesising glutamine from glutamate. The increased levels of glutamine lead to an increase in osmotic pressure in the astrocytes, which become swollen. There is increased activity of the inhibitory γ-aminobutyric acid (GABA) system, and the energy supply to other brain cells is decreased. This can be thought of as an example of brain edema of the "cytotoxic" type.

https://en.wikipedia.org/wiki/Hepatic_encephalopathy#Causes

get full access to all content ⋅ pick a username

+0 upvote downvote
submitted by ∗d_holles(218)

get full access to all content ⋅ pick a username

Can portal HTN contribute to hepatic encephalopathy?

get full access to all content ⋅ pick a username

djtallahassee Sorry for the late add. Portal system does contribute to hepatic enceph ESPECIALLY when there is a TIPS or shunt that bypasses the liver. However before, it won't directly contribute to more NH3+ +2

Must-See Comments from nbme22

sacredazn on Unrearranged immunoglobulin gene
seagull on Decreased binding of RNA polymerase
seagull on Anticholinergic
mcl on Area labeled ‘D’
liverdietrying on Release of stored thyroid hormone from a ...
kernicterusthefrog on Displacement
keycompany on Negative nitrogen balance
joha961 on Displacement
imgdoc on Area labeled ‘C’ (Abducens nucleus, right)
alwaysanonymous on 25 mL/cm H2O
drdoom on 1 in 600
seagull on Glutamine
yotsubato on Phase variation
bubbles on Acute retroviral infection