Differential Diagnosis
- Single most likely diagnosis:
- Diabetic Ketoacidosis (DKA): The patient's symptoms of polydipsia (drinking large quantities of fluids), polyuria (urinary frequency), significant weight loss, abdominal pain, nausea, vomiting, and a fruity odor to her breath are classic for DKA. The fruity odor is due to the presence of acetone, a volatile ketone body. DKA is a serious complication of diabetes mellitus, particularly type 1 diabetes, which often presents in childhood.
- Other Likely diagnoses:
- Gastroenteritis: Although less likely given the combination of symptoms, gastroenteritis could explain some of the gastrointestinal symptoms like abdominal pain, nausea, and vomiting. However, it wouldn't typically cause a fruity odor to the breath or significant weight loss over two months.
- Urinary Tract Infection (UTI): Could potentially explain urinary frequency but would not account for the full spectrum of symptoms, especially the metabolic disturbances suggested by the fruity odor and significant weight loss.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
- Appendicitis: Although the patient has diffuse abdominal tenderness, appendicitis typically presents with more localized pain (initially around the navel and then moving to the lower right abdomen). Missing appendicitis could lead to rupture and peritonitis, which are life-threatening.
- Intussusception: A condition where a part of the intestine slides into an adjacent part, potentially causing bowel obstruction. It's a pediatric emergency that could present with abdominal pain and vomiting but is less likely given the metabolic symptoms.
- Rare diagnoses:
- Other metabolic disorders: Such as organic acidemias or maple syrup urine disease, which could present with metabolic derangements and might have a distinct odor to the breath or urine. However, these are much rarer than DKA and would not typically cause the exact constellation of symptoms described.
- Chronic kidney disease: Could potentially explain some symptoms like polyuria and weight loss but would not account for the acute presentation or the fruity odor.
Given the options provided (A, B, C, D, E), the most likely additional finding in this patient, considering the context of DKA, would be C) Increased tidal volume, as patients with DKA often hyperventilate (Kussmaul breathing) in an attempt to compensate for the metabolic acidosis, leading to an increased tidal volume.