Clinical Picture

Differential Diagnosis and How to Rule Out Each

Investigations

1. Primary survey first (ABCDE) regardless of the isolated complaint — vitals, GCS, look for distracting injuries.
2. Bedside glucose + ketones/VBG immediately — because the question specifically flags diabetes, DKA must be excluded/treated in parallel with trauma workup.
3. FAST scan — rapid bedside screen for free fluid, but note it has limited sensitivity for hollow viscus and retroperitoneal injury (pooled sensitivity as low as ~35% in some studies), so a negative FAST does not exclude bowel/mesenteric injury.
4. Labs: CBC (serial Hb), U&E/creatinine, lactate, amylase/lipase, LFTs, coagulation profile, group & save/crossmatch, urinalysis (hematuria), beta-hCG if female.
5. CT abdomen and pelvis with IV contrast — the definitive investigation in a hemodynamically stable patient; look for free air, bowel wall thickening, mesenteric stranding/hematoma, free fluid without solid organ injury (suggests hollow viscus/mesenteric injury), fractures.
6. Pelvic X-ray and CXR as part of the trauma series.
7. Serial abdominal examinations over 6-24 hours — critical because bowel/mesenteric injury can be occult on the initial CT (Current Surgical Therapy, p. Blunt Injury; Rosen's Emergency Medicine).
8. Diagnostic laparoscopy or peritoneal lavage if CT is equivocal but clinical suspicion remains high.

Management

• Unstable + positive FAST → emergent laparotomy without waiting for CT.
• Stable patient → CT-directed selective non-operative management with admission for serial exams and repeat labs; this is now standard of care per EAST and the 2025 European Journal of Trauma and Emergency Surgery guideline update on abdominal injury management in multi-trauma patients (PMID: 40237811).
• If bowel/mesenteric injury or perforation confirmed → surgical consultation, laparotomy/laparoscopy with primary repair or bowel resection as needed; broad-spectrum antibiotics if perforation/contamination suspected.
• Glycemic control — correct any DKA or significant hyperglycemia (IV fluids, insulin infusion per protocol) in parallel; uncontrolled diabetes raises perioperative risk and impairs wound healing, so involve endocrinology early if surgery is anticipated.
• Supportive care: analgesia, NPO status pending workup, tetanus prophylaxis, VTE prophylaxis.
• Discharge criteria if imaging is negative: normalized serial exams, stable labs, resolving pain, tolerating oral intake — but given the diabetic neuropathy caveat, err toward a longer observation period before discharge in this patient.

Specific History Questions (organized by what each rules in/out)

• Speed of the bike and the car at impact, direction of impact (T-bone, head-on, rear-ended)
• Was he wearing a helmet? Any head strike or loss of consciousness, even brief? (rules out TBI as a confounder for unreliable abdominal exam)
• Was he thrown off the bike, dragged, or pinned under the vehicle/bike?
• Exact point of impact on the body — did the handlebar, fuel tank, or bike frame strike the abdomen/pelvis directly? (handlebar injuries classically cause duodenal hematoma, splenic/liver injury)
• Did he land on his right side or right flank?
• Time elapsed since the accident (progressive pain over hours suggests evolving hollow viscus injury or delayed bleed)

• Onset — immediate at impact or delayed/progressive since?
• Constant vs colicky, migration of pain (periumbilical shifting to RLQ raises appendicitis independent of trauma)
• Aggravated by movement, coughing, deep breathing, or tensing abdominal muscles (positive = wall source, e.g., rectus sheath hematoma, rather than intraperitoneal)
• Radiation to back (retroperitoneal/renal), flank, groin, or testicle (renal/ureteric/testicular)
• Any hematuria (even a pink tinge), reduced or no urine output since the accident

• Nausea, vomiting (and whether bilious/bloody), abdominal distension, absence of flatus/bowel movement since the accident, any melena or hematochezia

• Type of diabetes, duration, current medications — specifically ask if he is on metformin (relevant if CT contrast is planned — hold metformin around contrast administration if renal function unknown, due to lactic acidosis risk)
• Last dose of insulin/oral hypoglycemics and last meal (relevant for anesthesia risk if surgery needed, and for interpreting glucose)
• Baseline renal function if known (creatinine) — diabetics are at higher risk of contrast-induced nephropathy
• Any known peripheral or autonomic neuropathy, gastroparesis (autonomic neuropathy can blunt visceral pain and mask peritonism — this is exactly why his "no visible lesion" and possibly unimpressive exam cannot be trusted)
• Symptoms of DKA — excessive thirst, polyuria, deep/rapid breathing, fruity breath odor, vomiting before or after the accident (need to know if abdominal pain predates the crash, suggesting DKA rather than trauma)
• Any missed insulin doses recently, recent illness, or poor glycemic control

• Any prior abdominal surgery (adhesions change risk/appearance on imaging)
• Cardiac history — at 45-50 with diabetes, ask about chest pain, palpitations at time of impact (rule out a cardiac event as the cause of the crash itself, and assess fitness for potential surgery)
• Allergies (especially iodinated contrast), tetanus vaccination status, anticoagulant/antiplatelet use

Action Plan

• Airway, C-spine precautions, breathing, circulation (BP, HR, cap refill), full exposure to look for the seatbelt/handlebar sign, bruising, deformity
• eFAST at bedside as part of the primary survey

• Capillary/venous glucose + ketones or VBG right away (exclude DKA as a contributor, especially if pain preceded the crash)
• IV access x2, send bloods: CBC, U&E/creatinine, lactate, amylase/lipase, LFTs, coagulation, group & save/crossmatch, urinalysis for hematuria
• ECG (age 45-50 diabetic — also rules out a cardiac event that may have caused the crash)

• Head-to-toe exam including log-roll of the back, pelvic springing test (once, gently — avoid repeated pelvic compression if fracture suspected), genital and perineal inspection, Carnett's sign for the abdominal wall
• Document serial abdominal findings with timestamps — this is your safety net since diabetic neuropathy can mask evolving peritonism

• If hemodynamically unstable + positive FAST → skip further imaging, straight to theatre for laparotomy
• If stable → CT abdomen and pelvis with IV contrast (hold metformin if renal function unknown or impaired; check creatinine first if possible). Add pelvic X-ray/CXR if not already covered by CT.
• Look specifically for: free fluid without solid organ injury (bowel/mesenteric injury clue), bowel wall thickening, mesenteric stranding, free air, retroperitoneal hematoma, pelvic fracture, renal/splenic/hepatic injury

• Positive for hollow viscus/mesenteric injury, perforation, or peritonitis → surgical consult, laparotomy/laparoscopy, antibiotics
• Solid organ injury, stable → admit for non-operative management with serial Hb and exams
• CT negative but pain persists → admit for serial abdominal exams over 24 hours rather than discharging (do not rely on a single negative CT to exclude bowel injury, and do not let a diabetic patient's blunted symptoms falsely reassure you)
• DKA confirmed → start IV fluids and insulin infusion per protocol in parallel with trauma workup, involve medicine/endocrinology
• Correct glucose and optimize before any surgery if time permits, since hyperglycemia worsens surgical outcomes and wound healing