What are the differential diagnoses for a 16-year-old patient with type 1 diabetes mellitus (T1DM) presenting with vomiting?

Differential Diagnoses for a 16-Year-Old with Type 1 Diabetes Presenting with Vomiting

The most critical differential diagnosis is diabetic ketoacidosis (DKA), which must be ruled out immediately as it is a life-threatening emergency that commonly presents with vomiting in adolescents with type 1 diabetes. 1, 2

Life-Threatening Differentials (Evaluate First)

Diabetic Ketoacidosis (DKA)

• DKA is the primary concern in any type 1 diabetic patient presenting with vomiting, as approximately one-third of children with type 1 diabetes present with DKA, and it develops over hours to days 1
• Classic presentation includes polyuria, polydipsia, weight loss, dehydration, nausea, vomiting, abdominal pain, and Kussmaul respirations 1
• Vomiting accompanied by hyperglycemia and ketosis indicates DKA until proven otherwise 1, 2
• Check blood glucose immediately (typically >250 mg/dL but can be euglycemic), serum or urine ketones, venous pH (<7.3), and serum bicarbonate (<18 mEq/L) 3
• Vomiting is a characteristic symptom in type 1 DKA and distinguishes it from type 2 DKA presentations 4
• Hyperkalemia on initial presentation is more common in type 1 DKA compared to type 2 4

Hyperosmolar Hyperglycemic State (HHS)

• Less common in type 1 diabetes but can occur, especially in mixed presentations 1
• Develops over days to a week with more severe dehydration and altered mental status 1
• One-third of hyperglycemic emergencies have a hybrid DKA-HHS presentation 1

Metabolic/Endocrine Differentials

Hypoglycemia

• Can cause nausea and vomiting, especially if severe or with rapid glucose fluctuations 5, 6
• Check capillary blood glucose immediately (<60 mg/dL defines hypoglycemia) 1
• May occur from excessive insulin dosing, missed meals, or increased physical activity 6

Acute Hyperglycemia Without DKA

• Severe hyperglycemia alone (>200 mg/dL) can directly cause nausea and vomiting even without ketoacidosis 5, 7
• Marked hyperglycemia substantially slows gastric emptying, exacerbating nausea 5

Gastrointestinal Differentials

Diabetic Gastroparesis

• Affects 30-50% of patients with longstanding diabetes, though less common in adolescents 5
• Presents with nausea, vomiting, early satiety, and postprandial fullness 5
• Symptoms alone are poor predictors; requires objective testing with gastric emptying scintigraphy 5
• Can cause "gastric hypoglycemia" due to mismatched nutrient delivery and insulin action 5

Acute Gastroenteritis

• Common infectious cause presenting with vomiting, diarrhea, and abdominal pain 8
• Can precipitate DKA due to stress of illness and dehydration 1, 2
• Distinguish by presence of diarrhea, fever, and absence of severe hyperglycemia/ketosis 8

Acute Abdomen/Appendicitis

• Can mimic DKA presentation with vomiting and abdominal pain 8
• DKA itself can cause abdominal pain (45.3% of cases), making differentiation challenging 9
• Requires careful physical examination for peritoneal signs and imaging if indicated 8

Infectious Differentials

Infections (Most Common DKA Precipitant)

• Infections are the most common precipitating factor for DKA (73.33% of cases) 10
• Upper respiratory infections can trigger counter-regulatory hormone release, increasing insulin resistance and precipitating DKA 5
• Urinary tract infection presents with dysuria, frequency, and systemic symptoms 8
• Pneumonia presents with cough, dyspnea, fever, and chest findings 8
• Any infection increases insulin requirements and can lead to vomiting through direct illness effects 1, 2

Medication-Related Differentials

SGLT2 Inhibitor-Associated Euglycemic DKA

• Less common in type 1 diabetes but increasingly prescribed off-label 7
• Presents with DKA symptoms (nausea, vomiting, abdominal pain) but with near-normal or only mildly elevated glucose 3
• Must be stopped immediately if DKA suspected 7

Insulin Omission or Inadequate Dosing

• Main cause of DKA in established type 1 diabetes patients 4
• Inquire about insulin adherence, missed doses, or pump malfunction 1
• Only 23.3% of DKA patients were taking regular diabetes treatment in one study 10

Neurological Differentials

Central Nervous System Infection (Meningitis/Encephalitis)

• Can present with vomiting, altered mental status, and fever 8
• Requires evaluation for meningeal signs and consideration of lumbar puncture if suspected 8

Other Considerations

Eating Disorders

• Risk factor for recurrent DKA through intentional insulin omission 1
• More common in adolescent females with type 1 diabetes 1

Pregnancy (if applicable)

• Pregnancy increases DKA risk and alters insulin requirements 6
• Must be considered in female adolescents of childbearing age 6

Critical Initial Workup

Immediate bedside testing:

• Capillary blood glucose 1, 2
• Blood or urine ketones 1, 2
• Vital signs including mental status assessment 7

Laboratory evaluation:

• Venous blood gas (pH, bicarbonate) 3
• Complete metabolic panel (electrolytes, BUN, creatinine, glucose) 7, 3
• Serum ketones (preferred over urine) 1
• Anion gap calculation 3
• Complete blood count with differential 3
• Urinalysis 3
• Blood and urine cultures if infection suspected 3

Additional testing based on presentation:

• Chest radiography if respiratory symptoms 3
• Electrocardiography to assess for electrolyte abnormalities 3
• Amylase/lipase if severe abdominal pain 3
• HbA1c to assess chronic glycemic control 3

Common Pitfalls to Avoid

• Never assume vomiting is benign gastroenteritis without checking glucose and ketones in a type 1 diabetic 2
• Do not miss euglycemic DKA, especially if patient is on SGLT2 inhibitors or has been vomiting extensively 3
• Avoid attributing all symptoms to DKA without considering concurrent infections or acute abdomen 8
• Do not delay treatment while waiting for complete workup if DKA is suspected clinically 7
• Remember that abdominal pain in DKA can mimic surgical abdomen, but typically resolves with DKA treatment 9
• Recognize that altered mental status can be from DKA, hypoglycemia, or CNS infection - check glucose immediately 1, 8