Differential diagnosis

Differential diagnosis

Although acute appendicitis is the most common abdominal surgical emergency , the diagnosis can be extremely di ffi cult at times. There are a number of common conditions that it is wise to consider carefully and, if possible, exclude. The di ff erential diagnosis di ff ers in patients of di ff erent ages; in women, addi tional di ff erential diagnoses are diseases of the female genital tract ( Table 76.1 ). Children The diseases most commonly mistaken for acute appendicitis are acute gastroenteritis and mesenteric lymphad enitis . In mesenteric lymphadenitis, the pain is colicky in nature and cervical lymph nodes may be enlarged. It may be impossible to clinically 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 intermittent lower gastrointes tinal bleeding. 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 quad rant, and the preferred treatment of intussusception is reduc tion by careful barium enema. Henoch–Schönlein purpura is often preceded by a sore throat or respiratory infection. Abdominal pain can be severe and can be confused with intussusception or appendici tis. There is nearly always an ecchymotic rash, typically a ff ect ing 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. Microscopic haema turia is common. Johann Friedrich Meckel (the younger), 1781–1883, Professor of Anatomy and Surgery , Halle, Germany , described the diverticulum in 1809. Eduard Heinrich Henoch , 1820–1910, Professor of Diseases of Children, Berlin, Germany , described this form of purpura in 1868. Johann Lucas Schönlein , 1793–1864, Professor of Medicine, Berlin, Germany , described this form of purpura in 1837. Burrill Bernard Crohn , 1884–1983, gastroenterologist, Mount Sinai Hospital, New Y ork, NY , USA. Alexandre Emile Y ersin , 1863–1943, bacteriologist, Paris, France. 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 radio - graph is diagnostic. Adults Terminal ileitis in its acute form may be clinically indis - tinguishable from acute appendicitis unless a doughy mass of inflamed ileum can be felt. An antecedent history of abdominal cramping, weight loss and diarrhoea suggests regional ileitis rather than appendicitis. The ileitis may be non-specific, due to Crohn’s disease ( Figure 76.7 ) or Yersinia infection. Yersinia entero - - colitica causes inflammation of the terminal ileum, appendix and caecum with mesenteric adenopathy . If suspected, serum antibody titres are diagnostic, and treatment with intravenous tetracycline is appropriate. If Yersinia infection is suspected at operation, a mesenteric lymph node should be excised and divided, with half submitted for microbiological culture - (including tuberculosis) and half for histological examination. Ureteric colic does not commonly cause diagnostic dif - ficulty , as the character and radiation of pain di ff ers from that of appendicitis. Urinalysis should always be performed, and the presence of red cells should prompt a supine abdominal radiograph. A renal ultrasound or urogram will provide the - diagnosis. Right-sided acute pyelonephritis is accompanied and often preceded by increased frequency of micturition. It may cause di ffi culty in diagnosis, especially in women. The leading features are tenderness confined to the loin, fever (temperature - 39°C) and possibly rigors and pyuria. - In perforated peptic ulcer , the duodenal contents pass along the paracolic gutter to the right iliac fossa. As a rule there is a history of dyspepsia and a very sudden onset of pain that 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.

Adult female Elderly Mittelschmerz Diverticulitis Pelvic in /f_l ammatory disease Intestinal obstruction Pyelonephritis Colonic carcinoma Ectopic pregnancy Torsion appendix epiploicae Torsion/rupture of ovarian cyst Mesenteric infarction Endometriosis Leaking aortic aneurysm

An erect chest radiograph will show gas under the diaphragm in 70% of patients. An abdominal computed tomography (CT) examination is valuable when there is diagnostic di ffi culty . Testicular torsion in a teenage or young adult male is easily missed. Pain can be referred to the right iliac fossa, and shyness on the part of the patient may lead the unwary to sus pect appendicitis unless the scrotum is examined in all cases. Acute pancreatitis should be considered in the di ff er ential diagnosis of all adults suspected of having acute appen dicitis and, when appropriate, should be excluded by serum or urinary amylase measurement. Rectus sheath haematoma is a relatively rare but eas ily missed di ff erential 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 with out gastrointestinal upset is the rule. Occasionally , in an elderly patient, particular ly one taking anticoagulant therapy , a rectus sheath haematoma may present as a mass and tenderness in the right iliac fossa after minor trauma. Pelvic inflammatory disease comprises a spectrum of /uni00A0 diseases that include salpingitis, endometritis and tubo ovarian sepsis. The incidence of these conditions is increasing, and the diagnosis should be considered in every young adult female. Typically , the pain is lower than in appendicitis and is bilateral. A history of vaginal discharge, dysmenor rhoea and burning pain on micturition is a helpful di ff erential diagnos tic point. The physical findings include adnexal and cervical tenderness on vaginal examination. When suspected, a high vaginal swab should be taken for Chlamydia trachomatis Neisseria gonorrhoeae culture, and the opinion of a gynaecologist should be obtained (see Chapter 87 ). lower abdominal and pelvic pain, typically midcycle, which is characteristic of mittelschmerz . Systemic upset is rare, a pregnancy test is negative and symptoms usually subside within hours. Occasionally , diagnostic laparoscopy is required. Retro - grade menstruation may cause similar symptoms. T orsion or haemorrhage of an ovarian cyst can prove a di ffi cult di ff erential diagnosis. When suspected, pelvic ultrasound and a gynaecological opinion should be sought. 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 continues unabated until operation. Usually , there is a history of a missed menstrual period, and a urinary pregnancy test may be pos - itive. 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 referr ed pain in the shoulder. Pelvic ultrasonography should be carried out in all cases in which an ectopic pregnancy is a possible diagnosis. In some patients with a long sigmoid loop, the colon lies to the right of the midline and it may be impossible to di ff er - entiate between diverticulitis and appendicitis. Abdominal CT scanning is particularly useful in this setting and should be considered in the management of all patients over the age of 60 years. Right-sided diverticulitis is more common in Asia and may be clinically indistinguishable from appendicitis. Abdominal CT scanning is particularly useful in making the distinction. As with left-sided diverticulitis, treatment should - be conservative with intravenous antibiotics with recourse to laparoscopy or laparotomy in the face of clinical deterioration. - The diagnosis of intestinal obstruction is usually - clear; the subtlety lies in recognising acute appendicitis as the occasional cause in the elderly . An abdominal CT scan will clarify the diagnosis. - 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 and an abdominal CT scan 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. 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 aggra - and vated by movement. There is rigidity of the lumbar spine and intestinal symptoms are absent.

Figure 76.7 First presentation in a 19-year-old man with terminal ile itis, later con /f_i rmed to be Crohn’s disease. Short arrow demonstrates abnormally thickened and in /f_l amed terminal ileum. Long arrow indi cates wall enhancement and enlargement of the appendix, indicating secondary acute appendicitis (courtesy of Professor P MacMahon, FRCR, Dublin, Ireland).

need to be remembered. A urinalysis should be undertaken 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 but potentially fatal enterocolitis occurring in immunosuppressed patients. Gram-negative or clostridial (especially Clostridium septicum ) septicaemia can be rapidly progressive. Treatment is with appropriate antibiotics and haematopoietic factors. Sur gical intervention is rarely indicated.