Right Iliac Fossa Mass in a Young Woman
A 24-year-old woman presents with 36 hours of central abdominal pain migrating to the right iliac fossa, anorexia and one episode of vomiting. She is 8 weeks postpartum after an uncomplicated vaginal delivery and is breastfeeding. Temperature 37.9 C, HR 96, BP 118/72. Abdomen shows guarding and rebound tenderness in the right iliac fossa with a palpable, tender mass. WCC 15.2, CRP 88, urine dipstick has trace leucocytes but is nitrite negative. Beta-hCG is negative. Pelvic ultrasound shows a 6 cm complex right adnexal mass with internal echoes and a normal uterus. The on-call gynaecology registrar is unavailable for 4 hours and suggests 'admit for observation and repeat scan in the morning'.
1. Construct a differential diagnosis and explain how you would prioritise investigation and management in the next 4 hours.
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The differential includes appendicitis with a phlegmon or abscess, appendiceal mucocele or tumour, a ruptured or torsed ovarian cyst, tubo-ovarian abscess, ectopic pregnancy (excluded by negative beta-hCG), and less likely Crohn's disease, mesenteric adenitis or caecal malignancy.
The ultrasound finding of a 6 cm complex adnexal mass is not diagnostic; it may represent a haemorrhagic corpus luteum, a tubo-ovarian abscess or an endometrioma, and does not exclude appendicitis. Trace leucocytes with a negative nitrite make urinary tract infection unlikely.
Priorities:
- Do not accept simple observation. A tender mass with peritonism and rising inflammatory markers needs a definitive diagnosis.
- Request an urgent CT abdomen and pelvis with intravenous contrast; it is the best test to distinguish appendiceal pathology from adnexal disease and to identify an abscess or free fluid. If CT is unavailable or radiation is a concern, MRI is an alternative but slower.
- Send blood cultures, group and save, and repeat FBC/CRP in 6 hours.
- Start broad-spectrum intravenous antibiotics covering gram-negative and anaerobic organisms (for example ceftriaxone plus metronidazole), because a perforated appendix or tubo-ovarian abscess is possible.
- Analgesia and antiemetics; keep nil by mouth in case of surgery.
- Escalate to the consultant surgeon and gynaecologist rather than waiting for the registrar.
If CT shows appendicitis with a small abscess, percutaneous drainage plus antibiotics may allow interval appendicectomy; if it shows free perforation or generalised peritonitis, operate. If a tubo-ovarian abscess is confirmed, gynaecology drainage may be needed.
2. CT confirms a 3 cm appendiceal abscess with a phlegmon and no free gas. Discuss the options and defend your preferred management in this specific patient.
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Options are:
A. Immediate appendicectomy. Traditionally favoured for young fit patients, but in the presence of a well-formed abscess and phlegmon, dissection is technically difficult and carries higher rates of bowel injury, conversion to open surgery and wound infection.
B. Percutaneous drainage plus intravenous antibiotics, followed by interval appendicectomy. This is generally preferred when a drainable abscess (typically >3 cm) is present and the patient is stable without generalised peritonitis. It avoids an emergency operation in an inflamed field, shortens hospital stay and reduces complications.
C. Antibiotics alone. Reasonable for a small abscess (<3 cm) or phlegmon without a drainable collection, but this patient has a 3 cm collection and significant symptoms.
My preference: Image-guided percutaneous drainage with a course of intravenous antibiotics (for example ceftriaxone and metronidazole), converting to oral once afebrile and tolerating diet, then interval appendicectomy at 6-8 weeks.
Justification for this patient: She is postpartum and breastfeeding, so minimising anaesthetic and surgical risk and preserving lactation is valuable; she is haemodynamically stable without generalised peritonitis; the collection is drainable.
Caveats:
- If she develops generalised peritonitis, sepsis or failure to improve in 24-48 hours, proceed to surgery.
- Interval appendicectomy is debated; some argue it is unnecessary after successful non-operative management, but it allows histological exclusion of an appendiceal neoplasm, which is more common in adults with an appendiceal mass. Discuss this with her.
- Antibiotic choice must be compatible with breastfeeding; ceftriaxone and metronidazole are generally acceptable.
- Document shared decision-making.