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Gastrointestinal Disorders and Conditions for USMLE - Dr. Mike Mehlman

Overview of Gastrointestinal Disorders Affecting the Lips/Oral Cavity

Peutz-Jeghers Syndrome

Characterized by a combination of perioral melanosis (a term used to describe hyperpigmentation around the lips/mouth) and hamartomatous colonic polyps.
In USMLE examinations, students can expect an image of lips followed by a question regarding the types of polyps present in the colon. The answer to be provided is "hamartomatous".

Osler-Weber-Rendu Syndrome

Also known as hereditary hemorrhagic telangiectasia; transmitted in an autosomal dominant manner.
National Board of Medical Examiners (NBME) commonly presents images, such as of the mouth or fingernail to depict telangiectasias (small dilated blood vessels).
Clinical questions may include nosebleeds alongside visual aids, linking the syndrome to a potential risk for high-output cardiac failure due to pulmonary AV fistulae (abnormal connections between arteries and veins).
Gastrointestinal (GI) bleeding can occur, leading to anemia due to loss of blood.

Plummer-Vinson Syndrome

Defined by a triad of symptoms: 1. Iron deficiency anemia, 2. Esophageal webs leading to dysphagia, 3. Angular cheilitis (cracked corners of the mouth).
Questions may also reference pica (an eating disorder causing cravings for non-nutritive substances, such as clay or ice) or exhibit cases of koilonychia (spoon-shaped nails), indicating severe iron deficiency.

Miscellaneous Oral Conditions for USMLE

Lip Psoriasis

Can occur on the lips; USMLE may highlight the upper lip or forehead leading to confusion about the typical locations of psoriasis, which is usually on extensor surfaces.

Aphthous Ulcer

Commonly known as a canker sore.
Typically manifests as a painful, self-resolving lesion on the labial mucosa.
Non-infectious in nature and thought to have a mild autoimmune association; may have triggers, such as spicy foods.

Kawasaki Disease

A vasculitis presenting with 5 or more days of fever, conjunctival injection (red eyes), changes in the lips/tongue, cervical lymphadenopathy, edema on the dorsa of the hands, and desquamation of palms/soles (often confused with a rash).
Note: Students tend to fixate on coronary artery aneurysms as a high-yield point, which are rarely a focus of USMLE.

Perioral Impetigo

Often confused with herpes infection.
Common in children; usually presents with lip lesions due to infections from Staphylococcus aureus or Group A Streptococcus (S. pyogenes).
Can lead to post-streptococcal glomerulonephritis (PSGN) if caused by Strep.

Herpes Labialis

Caused by either HSV-1 or HSV-2; the USMLE does not differentiate between the two based on location.
The primary infection presents with fever and regional lymphadenopathy, while recurrences are generally less severe.
The virus undergoes latency within sensory nerves.
Students may be asked about viral structure, which is classified as "DNA, enveloped, linear" in USMLE questions; a common misconception is to confuse HSV with Hepatitis B Virus (HBV), which is classified as "DNA, enveloped, circular".
Treatment involves acyclovir, a DNA polymerase inhibitor that induces chain termination. Resistance occurs primarily due to alterations in thymidine kinase activity.

Scarlet Fever

Induced by Group A Streptococcus.
Presents as a "strawberry tongue" or red lips, coupled with a salmon-pink maculopapular rash on the body.
Treatment with penicillin is indicated to prevent rheumatic fever (type II hypersensitivity reaction) and can also lead to PSGN (type III hypersensitivity reaction).

Hand-Foot-Mouth Disease

Caused by Coxsackie A virus (an RNA virus belonging to the Picornaviridae family).
Spread commonly among pediatric populations but can also affect adults, particularly caregivers.
Key distinction from Coxsackie B virus, which may lead to dilated cardiomyopathy and other conditions like diabetes type I and pleurodynia.

Herpangina

Another manifestation caused by Coxsackie A.
Shown by oropharyngeal vesicles or sores, may coexist with hand-foot-mouth disease.

Koplik Spots

Distinctive features of measles (rubeola), appearing as white/blue-ish spots on the buccal mucosa.
Essential in differentiating measles from rubella.
Measles and rubella share a head-to-toe maculopapular rash but differ in specific lymphadenopathy findings: sub-occipital and post-auricular nodes for rubella.
The common triad of cough, coryza, and conjunctivitis is not exclusive to measles but instead, a general indicator for various viral infections, emphasizing the importance of diagnostic precision.

Sialolithiasis

Refers to the formation of stones within the ducts of the salivary glands.
Stensen duct is particularly noted, located near the second upper molar bilaterally, as the exit point of the parotid duct into the oral cavity.
Clinical scenarios may illustrate pain or inflammation on the buccal mucosa opposite the second upper molar, prompting considerations of sialadenitis (inflammation) or sialolithiasis.

Leukoplakia

Identified as a white-ish, painless, rough patch on the lateral tongue.
A significant precursor to squamous cell carcinoma of the tongue, with smoking and chewing tobacco identified as key risk factors.

Oral Hairy Leukoplakia

Similar in appearance to leukoplakia, but caused specifically by Epstein-Barr Virus (EBV).
Not classified as premalignant due to absence of dysplasia upon biopsy.

Oropharyngeal Candidiasis

Characterized by painless white plaques on the palate or tongue that bleed upon scraping.
Frequently observed in immunocompromised individuals, such as those with AIDS or organ transplant recipients on immunosuppressive therapy.
Can also occur in patients with asthma utilizing inhaled corticosteroids; patients are advised to rinse their mouths post-use to reduce candida risk.
Treatment options include nystatin mouthwash.
Odynophagia (painful swallowing) in an immunocompromised patient is often indicative of candidal esophagitis until proven otherwise, with management involving oral fluconazole (different from oral thrush which utilizes nystatin).

Salivary Gland Neoplasia

Pleomorphic Adenoma

This benign salivary gland tumor is characterized by variability in cell size and shape; often the answer given on USMLE questions regarding benign salivary gland tumors.
It is noted as the most common benign salivary gland tumor.
Classification of "pleomorphic" refers to the variability observed in the size and shape of cells and nuclei.

Mucoepidermoid Carcinoma

Malignant salivary gland tumor.
The most common malignant salivary gland tumor answer found on USMLE questions.
Distinguished by its ability to invade and the presence of B-symptoms (fever, night sweats, weight loss) associated with malignancy.

Warthin Tumor

This specific salivary gland tumor is noted for its resemblance to lymphatic tissue and often appears in cases where lymphoid stroma is mentioned in exam questions.

High-Yield Esophageal Conditions for USMLE

Hiatal Hernia

Involves the herniation of the stomach through the diaphragm.
The majority (95%) of cases are classified as a "sliding hiatal hernia," where the cardia of the stomach ascends through the esophageal hiatus into the thoracic cavity.
Described as an "abnormal relation of the cardia to the lower end of the diaphragm" within NBME questions.
The remaining 5% relate to paraesophageal hernias, where the fundus of the stomach protrudes through an opening in the diaphragm adjacent to the esophagus, defined by the phrase "protrusion of the fundus into the chest above the level of T10".
Hiatal hernias are correlated with gastroesophageal reflux disease (GERD).
Surgical intervention is typically not required.
Diagnosis often involves upper endoscopy, commonly tested on the 2CK Surgical exam.

Gastroesophageal Reflux Disease (GERD)

This condition arises from irritation of the esophageal mucosa by gastric acid, primarily attributed to decreased tone of the lower esophageal sphincter (LES).
Obesity is identified as a significant risk factor for GERD due to the strain and pressure it exerts on the LES.
The classic symptomatology includes burning sensation in the throat or chest post meals.
Additional presentations can include nocturnal cough or recurrent pneumonitis, which are crucial findings in patients who lack classic symptoms of esophageal irritation.
Pathology of GERD can lead to Barrett esophagus, a precursor to esophageal adenocarcinoma.
Initial diagnostic effort includes a 2-week trial of proton pump inhibitors (PPIs) such as omeprazole to alleviate symptoms.
PPIs, like esomeprazole, demonstrate greater efficacy in comparison to H2-blockers (e.g., cimetidine).
In cases where a PPI trial proves ineffective, the next step is 24-hour esophageal pH monitoring.
Nissen fundoplication is a last resort therapy mentioned on NBME examinations.

Barrett Esophagus

This condition is characterized by the metaplasia of the distal esophagus, represented by the conversion of non-keratinized stratified squamous epithelium to columnar epithelium featuring goblet cells (which secrete mucus).
It is often referred to as “intestinal columnar epithelium.” The stomach does not possess goblet cells; instead, it houses mucous neck (foveolar) cells.
Barrett esophagus is critically linked to increased risk of developing esophageal adenocarcinoma.
On upper endoscopy, Barrett esophagus may appear grossly red; the next step following visualization is to perform a biopsy to confirm the presence of Barrett metaplasia.

Esophageal Adenocarcinoma

This malignancy typically affects the lower third of the esophagus.
The high-yield pathogenesis sequence is aligned as follows: GERD → Barrett esophagus → adenocarcinoma.
Common presentation includes individuals older than 50 with a history of GERD, typically showing either of two key symptoms: 1) new-onset dysphagia for solids, or 2) dysphagia for solids that escalates to include liquids.
In both cases, the immediate next step is endoscopy, which should be favored over barium studies when symptomatic dysphagia is presented.
Occasionally, prompts may mention that an endoscopy revealed a stricture, followed by requiring identification of the next best step, which would be to biopsy the stricture.

Esophageal Squamous Cell Carcinoma

This condition primarily impacts the upper two-thirds of the esophagus, with heavy smoking and alcohol use regarded as the most significant risk factors.
The malignant process typically correlates with patients over 50 who present with abnormal dysphagia similar to adenocarcinoma, requiring urgent endoscopy followed by stricture or lesion biopsy.

Zenker Diverticulum

Characterized by an outpouching of the esophagus located above the cricopharyngeus muscle, just above the upper esophageal sphincter.
Various mechanisms such as spasm of the cricopharyngeal muscle, uncoordinated swallowing, dysphagia, and increased oropharyngeal pressure may be noted on USMLE.
It's defined as a false diverticulum, encompassing only mucosal and submucosal layers, while true diverticula, such as Meckel's diverticulum, include the muscular layer as well.
Typically seen in overweight males aged 40-50 presenting with gurgling sounds during swallowing or regurgitating undigested food; patients may exhibit halitosis (bad breath) mentioned in roughly one-third of questions.
Diagnosis is often via barium swallow study, while treatment primarily involves diverticulectomy.

Achalasia

Defined by abnormal tightness (elevated tone) of the LES attributed to loss of nitric oxide-secreting neurons found in the Auerbach (myenteric) plexus.
Current USMLE questions may refer to the problem in the "enteric ganglia".
Achalasia typically presents as dysphagia for both solids and liquids from the outset, differing from neoplastic dysphagia which usually starts with solids and progresses.
Generally idiopathic, though cases may occur secondary to Chagas disease.
USMLE may refer to this as “South American trypanosomiasis.”
The initial diagnostic step is a barium swallow, which shows a distinctive "bird’s beak" appearance, followed by esophageal manometry for confirmation.
Commonly, treatment methods include pneumatic dilation followed by myotomy for muscle fiber severance at the LES.

Systemic Sclerosis (Scleroderma)

An idiopathic autoimmune disorder characterized by multi-organ fibrosis leading to hardening of tissues.
Can contribute to GERD conditions, noted in an offline Step 1, with reductions in LES sphincter tone and diminished esophageal peristalsis.
This is related to the esophageal dysmotility from CREST syndrome (Calcinosis, Raynaud’s phenomenon, Esophageal dysmotility, Sclerodactyly, and Telangiectasias).

Esophageal Perforation

Can occur due to iatrogenic means (endoscopic procedures) or Boerhaave syndrome resulting from increased intrathoracic pressure due to retching or vomiting.
USMLE often specifies that water-soluble contrast swallowing reveals mediastinal accumulation. If not explicitly mentioned, cases may present recent endoscopy or straining linked with acute hypotension and tachycardia, leading to elimination of alternative responses by process of reasoning.
Water-soluble contrast agents (Gastrografin) are preferred for suspected perforation due to concerns that barium could induce mediastinitis.
In cases with aspiration risks, barium is appropriate, while Gastrografin can invoke pneumonitis.
The standard treatise in USMLE revolves around “esophageal repair.”

Mallory-Weiss Tear

Following retching or vomiting episodes in alcoholics, can lead to tearing of the gastroesophageal junction, often resulting in small bloody vomitus.
Also manifest in patients with eating disorders or hyperemesis gravidarum. The important note on this condition is that it does not generate high-volume hematemesis; if high-volume blood is reported, it signals a ruptured varix (discussed below).

Esophageal Varices

Represent enlarged, tortuous veins in the esophagus due to portal hypertension resulting from cirrhosis or splenic vein thrombosis.
In cirrhotic conditions, the left gastric vein connects esophageal veins with the portal vein, leading to pressure backflow into the left gastric vein, subsequently affecting esophageal veins.
USMLE frequently seeks "left gastric vein" as a key vessel responsible for variceal formations.
In splenic vein thrombosis contexts, elevated splenic venous pressure results in collateral formation to circumvent the obstruction, with left gastric veins contributing to increased esophageal venous pressure.
Approximately 80% of USMLE questions on varices indicate high-volume hematemesis; in contrast, Mallory-Weiss tears typically produce only minimal bleeding, reinforcing the notion that high-volume presentations strongly suggest variceal issues.
Ruptured varices carry a mortality rate of approximately 50%, frequently resulting in significant hemorrhage.
Propranolol serves as prophylaxis rather than acute treatment; the correct management involves endoscopic banding alongside management with Octreotide for acute bleeding situations.

Diffuse Esophageal Spasm

Idiopathic condition that causes esophageal spasms, mimicking angina pectoris without ongoing acute cardiac issues.
Barium swallow typically presents a corkscrew appearance.
Similarity with nutcracker esophagus due to heightened peristalsis causing similar discomfort.

Eosinophilic Esophagitis

An idiopathic allergic response affecting the esophagus resulting in dysphagia.
Biopsy findings typically demonstrate eosinophils within the epithelium.
Endoscopy visuals may show "trachealization" of the esophagus marked by concentric rings.
Past medical history may include asthma or other atopic conditions.

Schatzki Ring

Considered a less common diagnosis on USMLE and not frequently assessed as it tends to be described as a narrowing present only in distal esophagus while being indicative of differential diagnoses, primarily alongside achalasia.

High-Yield Gastrointestinal Exocrine Hormones

Exocrine Hormone Definition

Exocrine hormones refer to substances secreted directly across epithelium into the GI tract distinct from endocrine hormones that enter circulation directly.

Cholecystokinin (CCK)

Synthesized by neuroendocrine cells of the small bowel.
Acts to: 1. Induce gallbladder contraction, 2. Relax sphincter of Oddi, 3. Stimulate exocrine pancreatic secretion (proteases & lipases) into the duodenum.
Triggers for secretion are primarily macronutrients entering the duodenum post-pylorus, with fats recognized as the significant stimulant.
The mechanism of action should rely on the presence of macronutrients, as opposed to acidity, to initiate CCK secretion on the USMLE.

Secretin

Secreted by S cells of the duodenum, often less emphasized in USMLE questions.
Primarily prompts bicarbonate secretion from the exocrine pancreas into the duodenum, with input from acidity in the stomach as the stimulus for its release.
Expect line graphs showing pancreatic secretion trends: increased bicarbonate but no concomitant rise in enzyme levels.
In gastrinoma cases (Zollinger-Ellison syndrome), intriguingly, secretin does not induce the suppression of gastrin levels, which may confuse some students regarding its typical physiological interactions.

Histamine

Produced by enterochromaffin-like cells in the GI tract.
Binds H2 receptors on gastric parietal cells promoting increased acid secretion.
Hyperplasia of enterochromaffin-like cells commonly arises in chronic gastritis as a compensatory mechanism when parietal cells are destroyed or atrophied during the disease's evolution.
Cimetidine, a high-yield H2 blocker, reduces stomach acid secretion and may lead to gynecomastia or inhibitor-related increases in serum levels of various drugs due to inhibition of the P-450 enzyme system.
Ranitidine does not exhibit P-450 inhibition.

Gastrin

Released by G cells primarily in the stomach, promoting acid production via direct activation of gastrin receptors on parietal cells and stimulating enterochromaffin-like cells to release histamine for further acid secretion.
Gastrin levels typically ascend in cases of chronic gastritis and H. pylori infection.
Gastrinoma results in recurrent duodenal ulcers, with cases sometimes linked to multiple endocrine neoplasia (MEN 1).

Vasoactive Intestinal Peptide (VIP)

Increased secretion volume and water content in pancreatic secretions constitute its primary function.
Notably, VIPoma appears frequently on 2CK assessments, presenting as WDHA syndrome characterized by Watery Diarrhea, Hypokalemia, and Achlorhydria.
Approximately one-third of questions focus more generally on serum pH and hypokalemia presentations with flushing phenomena.

Motilin

This secretory hormone influences peristalsis in the absence of food.
Borborygmi (gurgling stomach sounds) can also be attributed to its effects. Evidence suggests that erythromycin may stimulate motilin receptors and improve gastrointestinal motility in patients suffering from gastroparesis.

Glucose-dependent Insulinotropic Peptide (GIP)

Also recognized as gastric inhibitory peptide, recognized as a crucial hormone in USMLE examinations.
It causes insulin release in response to the intake of oral macronutrients, not limited to carbohydrates. Key takeaways: GIP is what leads to more effective utilization of oral glucose compared to intravenous delivery due to the insulin spike that occurs when glucose is ingested orally.
Expect questions that involve scenarios where two people receive equal glucose doses, one orally and one intravenously, with GIP being the recognized stimulus for improved utilization of orally consumed glucose. Conversely, GIP also increases IV glucose utilization when concurrent small amounts of oral fatty acids are introduced.