When you see a child or young adult with a painful flexed hip, and about a week's history of fever, anorexia, pain, and swelling in his inguinal area, think of iliac adenitis. The infection may have reached his iliac nodes from his leg, his perineal area (including his genitalia), or his buttocks. The abscess lies near his psoas muscle; this goes into spasm and sharply flexes his hip, so that he will not let you extend it beyond 90[de], and he cannot walk. He has a tense, tender, hard mass in his iliac fossa, which is lower, and closer to his anterior iliac spine, than an appendix mass. You will probably be unable to elicit fluctuation, and only occasionally will you find the site of the primary infection. He has a moderate leucocytosis.
It is useful to distinguish ''periadenitis' without suppuration (common), which resolves on antibiotics and does not need drainage, from an iliac abscess (less common), which needs drainage and which can follow periadenitis, or pyomyositis of the iliopsoas, or be an extension from osteomyelitis of the spine. An appendix abscess is quite different, and is inside the peritoneum, whereas all these other conditions are outside it.
This condition (iliac abscess) is also known as iliac adenitis, deep inguinal adenitis, extraperitoneal iliac abscess, or suppurating deep iliac nodes. It has several important differential diagnoses, and is often misdiagnosed.
Fig. 5-10 A PAINFUL FLEXED HIP in an ill patient has a variety of differential diagnoses. A, his hip is typically more flexed than is shown here. B, an iliac abscess forms in the iliac nodes. C, exploring extraperitoneally for iliac suppuration. D, the incision for an iliac abscess. C, and D, after ''Hamilton Bailey's Emergency Surgery', edited by Dudley HAF. John Wright with kind permission.
ILIAC ABSCESSES THE DIFFERENTIAL DIAGNOSIS is that of the ''sick child with the painful flexed hip'. It is more difficult if his right hip is flexed, because the diagnosis on this side includes appendicitis.
Suggesting iliac adenitis with periadenitis or an abscess[md]a septic lesion on the skin which may be minimal and have healed (adenitis may appear 2 weeks after the primary lesion has settled), a markedly flexed hip with a short history, a mass in his groin or right iliac fossa just above his inguinal ligament, no pain when you percuss his greater trochanter; you can flex his hip a bit more, no spasm of his sacrospinalis, and no X-ray changes.
Suggesting pyomyositis of his iliopsoas[md]the same signs as iliac adenitis. The differential diagnosis may be impossible, and is not important because the treatment is the same.
Suggesting an appendix abscess[md]a different anatomical site intraperitoneally in his right iliac fossa, nausea and vomiting, less spasm, and only mild flexion of his hip.
Suggesting septic arthritis of his hip[md]severe joint spasm, acute pain on percussing his greater trochanter, no palpable mass, and an X-ray showing a widened joint space. No movement of his hip due to severe pain. This is also osteomyelitis because the epiphyseal plate is inside the capsule of the hip joint.
Suggesting tuberculosis of his hip[md]a subacute history and X-ray signs of tuberculosis (29.1).
Suggesting a tuberculous psoas abscess arising from his spine[md]a subacute history, X-ray changes in his spine. A psoas abscess does not usually need drainage, unless it is very large and causing pain. It will resolve slowly on chemotherapy for tuberculosis; incising it can lead to secondary infection.
Suggesting acute and usually staphylococcal osteomyelitis of his spine (uncommon)[md]more pain, spasm of his sacrospinalis, X-ray signs in his spine. Drain the lesion as for osteomyelitis (7.2).
Other possibilities include Perthes' disease (27.14), a slipped epiphysis (77.10), and a fracture (77.1).
If the diagnosis is difficult, and you suspect an abscess, you can:
(1) Examine him under anaesthesia, with his abdominal muscles relaxed. Feel the exact site of the mass and its consistency and boundaries, and feel for fluctuation.
(2) Make a 4 cm oblique skin incision, medial to his anterior superior iliac spine, and aspirate the mass with a large-bore needle.
NON-OPERATIVE TREATMENT. Deep inguinal (iliac) adenitis with periadenitis and without pus formation does not require drainage. His hip is flexed as when an abscess is present. You can feel deep tender glands above his inguinal ligament. Give him an antibiotic (penicillin or chloramphenicol). If infection is slow to resolve, use skin traction (1/7th of his bodyweight, 70.10) and raise the foot of his bed.
DRAINAGE. If you have aspirated pus with a needle, you can safely open up the deeper layers. The abscess will have pushed the peritoneal lining of his right iliac fossa medially and superiorly. Make an incision 5 to 10 cm or more over the swelling about 2 cm above his inguinal ligament, starting just medial to his anterosuperior iliac spine (D, 5-10). Take a long haemostat and push this through the muscle over the abscess until you find pus. Then, using your fingers, enlarge the opening until it will take 3 or 4 of them.
Take a specimen, drain the lesion, and continue antibiotics.
If his leg remains in spasm, apply traction as above.
CAUTION ! Draining an iliac abscess is potentially dangerous[md]you may injure his caecum or his iliac vessels. So follow the method above and aspirate first.