13.1 Gastrointestinal Diagnosis

The current FNP-BC Test Content Outline scores Gastrointestinal as one of the 13 body systems. Domain II asks you to select diagnostics, interpret them, and formulate differentials. Implementation (Section 13.2) is what you prescribe after the name is right. This section is the diagnostic chapter: do not start a proton-pump inhibitor, an antispasmodic, or a gluten-free diet until the syndrome and the first test are clear.

GERD versus dyspepsia versus PUD versus cardiac chest pain

GERD is a reflux syndrome. Typical symptoms are heartburn and regurgitation, worse after meals or recumbency, sometimes with chronic cough, hoarseness, or a sour taste. In a younger adult with classic symptoms and no alarm features, a time-limited empiric PPI trial is acceptable diagnosis-and-treatment in one move. Extraesophageal complaints (asthma, laryngitis, globus) are less specific; do not label every cough as GERD without a pulmonary and ENT differential.

Dyspepsia is epigastric pain or burning, postprandial fullness, or early satiety. It is not a synonym for heartburn. Functional dyspepsia is a compatible pattern after you have excluded structural disease when the pretest risk warrants it. Peptic ulcer disease (PUD) is a mucosal break, usually from H. pylori or NSAIDs/aspirin. Ulcer pain may be burning and meal-related, and it can stay silent until bleeding. You cannot reliably separate “gastritis,” functional dyspepsia, and ulcer from the history alone — that is why H. pylori testing and endoscopy rules exist.

Cardiac ischemia is the chest-pain mimic that kills. Exertional pressure, radiation to the arm or jaw, diaphoresis, dyspnea, and atherosclerotic risk belong in an ACS pathway, not a GI cocktail with a 48-hour follow-up. A GI cocktail that “helps” does not exclude coronary disease. When the story could be either, treat it as cardiac first.

Alarm features mean endoscopy

Do not keep stacking PPIs when the history is a red flag. Alarm features that should move an adult toward prompt upper endoscopy (and often same-day labs) include dysphagia, odynophagia, gastrointestinal bleeding (hematemesis, melena, hematochezia), iron-deficiency anemia, unexplained weight loss, persistent vomiting, and a new dyspepsia presentation at age 60 or older. Progressive solid-food dysphagia is a structural warning (stricture, Schatzki ring, eosinophilic esophagitis, or cancer), not “more omeprazole.” Odynophagia raises infectious esophagitis (candida, HSV, CMV) in the immunosuppressed. Bleeding and anemia are not “watch the stool and recode as GERD.”

If the patient is hemodynamically unstable, orthostatic, or actively bleeding, the destination is the emergency department, not an outpatient EGD order with a two-week wait. Check a CBC, and think type-and-cross and resuscitation while you arrange transfer.

H. pylori: test-and-treat versus test-and-scope

For uninvestigated dyspepsia in adults younger than 60 without alarm features, the usual primary-care strategy is test-and-treat: a urea breath test or stool antigen (not IgG serology, which cannot distinguish old from active infection), then treat if positive. Test-and-scope (endoscopy first) is for age 60 or older, alarm features, failed noninvasive management, or when you need a tissue diagnosis. Do not use IgG serology to decide treatment in a previously treated patient, and do not skip eradication confirmation after therapy (Section 13.2). Stop PPIs about 1–2 weeks before breath or stool testing when you can; recent antibiotics and bismuth also cause false negatives.

A 42-year-old with isolated epigastric burning, no weight loss, and a normal CBC is a test-and-treat candidate. A 67-year-old with the same burning plus a falling hemoglobin is a scope candidate. Age and alarms change the algorithm; the pain adjective does not.

IBS versus IBD

Irritable bowel syndrome is a positive diagnosis, not a six-month exclusion tour. Rome-style criteria: recurrent abdominal pain at least 1 day per week in the last 3 months, associated with two or more of relation to defecation, change in stool frequency, or change in stool form, with symptom onset at least 6 months earlier. After a limited workup — CBC, age-appropriate colorectal-cancer screening, celiac serology (especially diarrhea-predominant IBS), and a CRP or fecal calprotectin when inflammation is in the differential — you treat IBS as IBS. You do not CT every cramp.

IBD (Crohn disease, ulcerative colitis) announces itself with inflammatory red flags: nocturnal diarrhea, visible blood, unintentional weight loss, fever, iron-deficiency anemia, elevated CRP or fecal calprotectin, oral ulcers, or extra-intestinal clues (uveitis, pyoderma, axial arthritis). Those findings are a GI referral and endoscopic evaluation, not another fiber handout. Normal inflammatory markers do not 100% exclude mild IBD, but abnormal markers plus a red-flag history should stop the “functional” label.

Viral hepatitis: presentation and who to test

Hepatitis A is fecal-oral, acute, and does not become chronic. Think travel, contaminated food, homelessness or unstable-housing clusters, and MSM networks. Prodrome then jaundice, dark urine, and a marked ALT/AST rise. Diagnosis is IgM anti-HAV. Management is supportive plus public-health reporting and vaccination of contacts as indicated.

Hepatitis B is blood and sexual. Acute disease looks like any viral hepatitis; chronic infection may stay silent until cirrhosis or hepatocellular carcinoma. Screen with a three-test panel when indicated (HBsAg, anti-HBs, anti-HBc). Vaccinate the uninfected. Chronic HBV is specialty comanagement, not an FNP-only nucleoside start from memory.

Hepatitis C is often asymptomatic for years. USPSTF recommends one-time HCV screening for all adults aged 18–79, with repeat testing when ongoing risk remains (injection drug use, HIV, hemodialysis). Screen with HCV antibody; confirm with HCV RNA. A positive antibody after treated or spontaneously cleared infection is not viremia — you need the RNA. Direct-acting antivirals are highly effective; the FNP’s job is case-finding, confirmation, HAV/HBV vaccination if susceptible, alcohol counseling, and linkage to a treating clinician.

Biliary disease: stones, colic, cholecystitis, cholangitis

Asymptomatic gallstones found on imaging done for another reason are usually observed. Biliary colic is episodic, severe right-upper-quadrant or epigastric pain, often after a fatty meal, lasting hours, without fever and with a nonperitoneal exam; labs are normal or nearly so; ultrasound shows stones. Elective surgical referral is reasonable for recurrent colic.

Acute cholecystitis is persistent pain plus inflammatory signs: fever, Murphy sign, leukocytosis, and ultrasound with wall thickening, pericholecystic fluid, or a sonographic Murphy. This is urgent surgical evaluation, not a three-day wait for the next GI slot.

Ascending cholangitis is a duct-obstruction infection. Charcot triad is RUQ pain, jaundice, and fever. Reynolds pentad adds hypotension and altered mentation. That patient belongs in the ED for antibiotics, resuscitation, and biliary decompression, not an oral fluoroquinolone from clinic.

Appendicitis, diverticulitis, and small-bowel obstruction

Appendicitis classically migrates from periumbilical to RLQ, with anorexia, low-grade fever, and McBurney tenderness. Pregnancy and children are less classic. Unstable or clearly surgical abdomens go to the ED. Imaging is ultrasound first in children and pregnancy, CT in most nonpregnant adults.

Diverticulitis in Western adults is usually LLQ pain, fever, and a change in bowel habit. CT confirms and grades complications (abscess, perforation, fistula). Uncomplicated, reliable patients may be managed as outpatients with close follow-up per current surgical guidance; peritonitis, inability to take oral intake, immunosuppression, or diagnostic uncertainty is ED/hospital. Do not treat every older adult with LLQ pain as “another UTI.”

Small-bowel obstruction presents with colicky pain, vomiting, obstipation, and often a prior laparotomy. Listen for high-pitched rushes; look for distention. This is ED imaging and surgical consultation, not an office enema and a phone check in the morning.

Constipation versus overflow

Functional constipation is infrequent, hard, or incomplete stools. Overflow (encopresis in children; fecal impaction in older or opioid-treated adults) presents as loose stool leaking around a hard mass. The trap is diagnosing “diarrhea” and giving loperamide. Do a digital rectal exam when anatomically appropriate, consider an abdominal radiograph if the exam is equivocal, and disimpact before you escalate antidiarrheals.

Celiac disease: test before the diet

Test when there is chronic diarrhea, iron-deficiency anemia, bloating, dermatitis herpetiformis, type 1 diabetes, autoimmune thyroid disease, a first-degree relative with celiac disease, or unexplained transaminase elevation. First-line serology is tissue transglutaminase IgA (tTG-IgA) plus a total IgA so you do not miss IgA deficiency. The patient must still be eating gluten. A self-started gluten-free diet can normalize serology and biopsies and delay the diagnosis for years. Confirm with small-bowel biopsy arranged by GI when serology is positive or suspicion remains high. HLA-DQ2/DQ8 is a rule-out tool in selected cases, not a stand-alone diagnosis.

Pancreatitis is an emergency-department diagnosis

Suspect acute pancreatitis with severe, persistent epigastric pain radiating to the back, nausea, and vomiting, especially with gallstones or heavy alcohol use. Diagnosis needs two of three: typical pain, lipase (or amylase) more than three times the upper limit, and characteristic imaging. This is ED care: NPO, fluids, analgesia, an etiology hunt (lipase, LFTs, ultrasound for stones), and admission. Do not send a lipase “to come back tomorrow” on a writhing patient. Recurrent or unexplained pancreatitis needs GI follow-up after the acute episode; chronic pancreatitis is a pain-and-malabsorption syndrome, not a clinic PPI problem.

FNP vignette trap: a 58-year-old on daily ibuprofen with epigastric pain and a hemoglobin of 9.2 g/dL is bleeding PUD until scoped, not “dyspepsia, increase the PPI.” A 34-year-old with Rome-positive IBS-D, a normal CBC, a normal calprotectin, and a positive tTG-IgA has celiac until biopsied, not “start dicyclomine.” A 71-year-old with fever, jaundice, and RUQ pain has cholangitis, not biliary colic.