Differential diagnosis
Although acute appendicitis is the most common
abdominal surgical emergency, the diagnosis at times can be extremely difficult.
It is important to remember that many conditions which mimic appendicitis also
require surgical intervention, or if they do not are rarely made worse by
appendicectomy. However, there is a number of common conditions that it is wise
to consider carefully and, where possible, exclude. The differential diagnosis
differs in patients of different ages and in adult life, females have the added
differential of diseases of the female genital tract (Table 59.5).
Children
The diseases most commonly mistaken for acute
appendicitis are acute gastroenteritis and
mesenteric lymphadenitis. In acute
gastroenteritis there is intestinal colic together with diarrhoea and vomiting,
but localised tenderness does not usually occur. There is often a history of
other family members being affected. Post ileal appendicitis may mimic this
condition, thus hospital admission and careful observation are warranted. Where
serious doubt persists laparoscopy or surgical exploration may be indicated. In
mesenteric
It
may be impossible clinically to distinguish Meckel’s
diverticulitis from acute appendicitis. The pain is similar, however signs
may be central or left-sided. Occasionally, there is a history of antecedent
abdominal pain or anaemia.
It
is important to distinguish between acute appendicitis and intussusception.
Appendicitis is uncommon before the age of 2 years, whereas the median age
for intussusception is 18 months. A mass may be palpable in the right lower
quadrant and the preferred treatment of intussusception is reduction by careful
barium enema.
Henoch—Schönlein purpura
This is often preceded by a sore throat or
respiratory infection. Abdominal pain can be severe and be confused with
intussusception or appendicitis. There is nearly always an ecchymotic rash,
typically affecting the extensor surfaces of the limbs and on the buttocks. The
face is usually spared. The platelet count and bleeding time are within normal
limits.
Lobar pneumonia and pleurisy
Lobar pneumonia and pleurisy, especially at
the right base, may give rise to right-sided abdominal pain and mimic
appendicitis. Abdominal tenderness is minimal, pyrexia is marked and chest
examination may reveal a pleural friction rub or altered breath sounds on
auscultation. A chest radiograph is diagnostic.
Adults
Terminal ileitis
Ureteric colic
Ureteric colic does not commonly cause
diagnostic difficulty as the character and radiation of pain differ from those
of appendicitis. Urinalysis should always be performed and the presence of red
cells should prompt a supine abdominal X-ray. Renal ultrasound or an intravenous
urogram is diagnostic.
Right-sided acute pyelonephritis
This is accompanied and often preceded by
increased frequency of micturition. It may cause difficulty in diagnosis,
especially in women. The leading features are tenderness confined to the loin,
fever (temperature 390C), and possibly rigors and pyuria.
Perforated peptic ulcer
(Duodenal contents pass along the paracolic
gutter to the right iliac fossa.) There is usually a history of dyspepsia and a
very sudden onset of pain, which
starts in the epigastrium and passes down the right paracolic gutter. In
appendicitis the pain starts classically in the umbilical region. Rigidity and
tenderness in the right iliac fossa are present in both conditions, but in
perforated duodenal ulcer the rigidity is usually greater in the right
hypochondrium. Radiography may show gas under the diaphragm. continues
unabated until operation. Usually there is a history of a missed menstrual
period and urinary pregnancy test may be positive. Severe pain is felt when the
cervix is moved on vaginal examination. Signs of intraperitoneal bleeding usually
become apparent and the patient should be questioned specifically regarding
referred pain in the shoulder. Pelvic ultrasonography should be carried out in
all cases where an ectopic pregnancy is a possible diagnosis.
Testicular torsion
Testicular torsion in a teenager or young adult male is easily missed.
Pain can be referred to the right iliac fossa, and shyness on the part of
patient may lead the unwary to suspect appendicitis unless the scrotum is
examined in all cases.
Acute pancreatitis
Acute pancreatitis should be considered in the differential diagnosis of
all adults suspected of acute appendicitis and when appropriate excluded by
serum or urinary amylase measurement.
Rectus sheath haematoma
This is a relatively rare but easily missed differential diagnosis. It
usually presents with acute pain and localised tenderness in the right iliac
fossa, often after an episode of strenuous physical exercise. Localised pain
without gastrointestinal upset is the rule. Occasionally, in an elderly patient,
particularly those on anticoagulant therapy, a rectus sheath haematoma may
present with a mass and tenderness in the right iliac fossa following minor trauma (Fig.
59.10).
Adult females
It is in women of child-bearing age that pelvic disease most often mimics
acute appendicitis. A careful gynaecological history should be taken in all
women with suspected appendicitis concentrating on menstrual cycle, vaginal
discharge and possible pregnancy. The most common diagnostic mimics are
salpingitis, mittelschmerz, torsion or haemorrhage of an ovarian cyst and
ectopic pregnancy.
Salpingitis
This is the condition which poses greatest diagnostic difficulty in
young women. Typically, the pain is lower than in appendicitis and is bilateral.
A history of vaginal discharge, dysmenorrhoea and burning pain on micturition
are all helpful differential diagnostic points. There may be a history of
contact with sexually transmitted disease. When suspected, the opinion of a
gynaecologist should be obtained, and high vaginal swab taken for Chlamydia culture.
When serious diagnostic uncertainty persists, diagnostic laparoscopy should be
undertaken.
Mittelschmerz
Midcycle rupture of a follicular cyst with bleeding produces lower
abdominal and pelvic pain, typically midcycle. Systemic upset is rare,
pregnancy test is negative and symptoms usually subside within hours.
Occasionally, diagnostic laparoscopy is required.
Torsion/haemorrhage of an ovarian cyst
This can prove a difficult differential diagnosis. When suspected,
pelvic ultrasound and a gynaecological opinion should be sought. If encountered
at operation, ovarian cystectomy should be performed, if necessary, in women of
child-bearing years. Documented visualisation of the contralateral ovary is an
essential medicolegal precaution.
Ectopic pregnancy
It is unlikely that a ruptured ectopic pregnancy, with its well-defined signs of
haemoperitoneum, will be mistaken for acute appendicitis, but the same cannot be
said for a right-sided tubal abortion, or still more for a right-sided
unruptured tubal pregnancy. In the latter, the signs are very similar to those
of acute appendicitis, except that the pain commences on the right side and stays there. The pain is
severe and
Elderly
Sigmoid diverticulitis
In some patients with a long sigmoid loop, the
colon lies to the right of the midline and it may be impossible to differentiate
between diverticulitis and appendicitis. A trial of conservative management with
intravenous fluids and antibiotics is often appropriate, with a low threshold
for exploratory laparotomy in the face of deterioration or lack of clinical
response.
Intestinal obstruction
The diagnosis of intestinal obstruction is
usually clear, the subtlety lies in recognising acute appendicitis as the occasional
cause in the elderly. As with diverticulitis, intravenous fluids, antibiotics
and nasogastric decompression should be instigated with early resort to
laparotomy.
Carcinoma of the caecum
When obstructed or locally perforated,
carcinoma of the caecum may mimic or cause obstructive appendicitis in adults.
A history of antecedent discomfort, altered bowel habit or unexplained anaemia
should raise suspicion. A mass may be palpable (vide infra) and barium enema or colonoscopy is diagnostic.
Rare differential diagnoses
Preherpetic
pain of the right 10th and 11th dorsal nerves is
localised over the same area as that of appendicitis. It does not shift and is
associated with marked hyperaesthesia. There is no intestinal upset or rigidity.
The herpetic eruption may be delayed for 3—8 hours. Tabetic
crises are now rare. Severe abdominal pain and vomiting usher in the crisis.
Other signs of tabes confirm the diagnosis. Spinal conditions are sometimes associated with acute abdominal
pain, especially in children and the elderly. These may include tuberculosis of
the spine, metastatic carcinoma, osteoporotic vertebral collapse and multiple
myeloma. The pain is due to compression of nerve roots and may be aggravated by
movement. There is rigidity of the lumbar spine and intestinal symptoms are
absent. The abdominal crises of porphyria
and diabetes mellitus need to he remembered. A urinalysis should be tested
in every abdominal emergency. In cyclical
vomiting of infants or young children there is a history of previous similar
attacks, and abdominal rigidity is absent. Acetone is found in the urine but is
not diagnostic as it may accompany starvation. Typhlitis
or leukaemic ileocaecal syndrome is a rare hut potentially fatal
enterocolitis occurring in immunosuppressed patients. Gram-negative or clostridial
(especially C. septicum) septicaemia
can be rapidly progressive. Treatment is with appropriate antibiotics and
haematopoetic factors. Surgical intervention is rarely indicated.