Right iliac fossa mass

What on earth is that lump?

You have a young patient screaming in pain “my appendix!“, but her mother is much more worried that it might be cancer. You ask her why she thinks he has cancer, and she says

  • appendix mass
  • caecal carcinoma

“He’s had diarrhoea that floats!” to which you reply “Sounds more like Crohn’s…”

  • Crohn’s

You’re interrupted by the patient, who is now convinced her ovaries are exploding and her intestine is eating itself.

  • Ovarian mass
  • Intussusception

Do you think it could be her transplant?” asks the mother quietly – this surprises you so you look at the patient’s abdomen for scars, but instead you see a huge pulsating lump that looks like an aneurysm of some sort.

  • Pelvic kidney
  • Common iliac aneurysm

Have you had a fever?” ¬†you ask? You’re thinking it could be an infection, either TB or an abscess.

  • Iliocaecal TB
  • Iliac lymphadenitis
  • Actinomycosis
  • Psoas abscess

The patient shakes her head, you then ask “can you push it back in?

  • Spigelian hernia

Both mother and daughter look at you like you’re an idiot, before daughter wets herself all over the bed. “What’s wrong with my bladder?” Which makes you think of her other bladder.

  • Gall bladder enlargement

The differential diagnosis for a right iliac fossa mass includes the following:

  • Appendix mass
  • Caecal carcinoma
  • Crohn’s disease
  • Ovarian mass
  • Intussusception
  • Pelvic kidney
  • Enlarged gall bladder
  • Iliocaecal TB
  • Iliac lymphadenitis
  • Psoas abscess
  • Retroperitoneal tumour
  • Actinomycosis
  • Common iliac artery aneurysm
  • Spigelian hernia

Clearly the likelihood of each is going to depend on the patient, the history, and the presentation. Caecal carcinoma is much more common in an elderly person than a teenager, while appendicitis is less likely if the patient has already had an appendicectomy…

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