Accuracy of MRI compared with ultrasound imaging and selective use of CT to discriminate simple from perforated appendicitis

Acute appendicitis: modern understanding of pathogenesis, diagnosis, and management

Acute appendicitis is one of the most common abdominal emergencies worldwide. The cause remains poorly understood, with few advances in the past few decades. To obtain a confident preoperative diagnosis is still a challenge, since the possibility of appendicitis must be entertained in any patient presenting with an acute abdomen. Although biomarkers and imaging are valuable adjuncts to history and examination, their limitations mean that clinical assessment is still the mainstay of diagnosis. A clinical classification is used to stratify management based on simple (non-perforated) and complex (gangrenous or perforated) inflammation, although many patients remain with an equivocal diagnosis, which is one of the most challenging dilemmas. An observed divide in disease course suggests that some cases of simple appendicitis might be self-limiting or respond to antibiotics alone, whereas another type often seems to perforate before the patient reaches hospital. Although the mortality rate is low, postoperative complications are common in complex disease. We discuss existing knowledge in pathogenesis, modern diagnosis, and evolving strategies in management that are leading to stratified care for patients.

Scoring system to distinguish uncomplicated from complicated acute appendicitis

Background

Non-operative management may be an alternative for uncomplicated appendicitis, but preoperative distinction between uncomplicated and complicated disease is challenging. This study aimed to develop a scoring system based on clinical and imaging features to distinguish uncomplicated from complicated appendicitis.

Methods

Patients with suspected acute appendicitis based on clinical evaluation and imaging were selected from two prospective multicentre diagnostic accuracy studies (OPTIMA and OPTIMAP). Features associated with complicated appendicitis were included in multivariable logistic regression analyses. Separate models were developed for CT and ultrasound imaging, internally validated and transformed into scoring systems.

Results

A total of 395 patients with suspected acute appendicitis based on clinical evaluation and imaging were identified, of whom 110 (27·8 per cent) had complicated appendicitis, 239 (60·5 per cent) had uncomplicated appendicitis and 46 (11·6 per cent) had an alternative disease. CT was positive for appendicitis in 284 patients, and ultrasound imaging in 312. Based on clinical and CT features, a model was created including age, body temperature, duration of symptoms, white blood cell count, C-reactive protein level, and presence of extraluminal free air, periappendiceal fluid and appendicolith. A scoring system was constructed, with a maximum possible score of 22 points. Of the 284 patients, 150 had a score of 6 points or less, of whom eight (5·3 per cent) had complicated appendicitis, giving a negative predictive value (NPV) of 94·7 per cent. The model based on ultrasound imaging included the same predictors except for extraluminal free air. The ultrasound score (maximum 19 points) was calculated for 312 patients; 105 had a score of 5 or less, of whom three (2·9 per cent) had complicated appendicitis, giving a NPV of 97·1 per cent.

Conclusion

With use of novel scoring systems combining clinical and imaging features, 95 per cent of the patients deemed to have uncomplicated appendicitis were correctly identified as such. The score can aid in selection for non-operative management in clinical trials.

Intra-abdominal sepsis--epidemiology, aetiology and management

Peritonitis is a progressive disease leading inexorably from local peritoneal irritation to overwhelming sepsis and death unless this trajectory is interrupted by timely and effective therapy. In children peritonitis is usually secondary to intraperitoneal disease, the nature of which varies around the world. In rich countries, appendicitis is the principal cause whilst in poor countries diseases such as typhoid must be considered in the differential diagnosis. Where resources are limited, the clinical diagnosis of peritonitis mandates laparotomy for diagnosis and source control. In regions with unlimited resources, radiological investigation, ultrasound, CT scan or MRI may be used to select patients for non-operative management. For patients with appendicitis, laparoscopic surgery has achieved results comparable to open operation; however, in many centres open operation remains the standard. In complicated peritonitis "damage control surgery" may be appropriate wherein source control is undertaken as an emergency with definitive repair or reconstruction awaiting improvement in the patient's general condition. Awareness of abdominal compartment syndrome is essential. Primary peritonitis in rich countries is seen in high-risk groups, such as steroid-dependent nephrotic syndrome patients, whilst in poor countries the at-risk population is less well defined and the diagnosis is often made at surgery.