Acute appendicitis is the most common surgical emergency in children and adults, and can result in extreme inflammation and perforation of the appendix, necessitating prompt surgical removal (appendicectomy).

As the condition can be challenging to differentiate from other causes of acute abdominal pain, diagnostic imaging is routinely used as an adjunct to clinical examination for suspected cases of appendicitis. 

Surveying data from 1,359 children who were admitted to KK Women’s and Children’s Hospital (KKH) for abdominal pain from January to December 2013, clinician researchers from KKH and Yong Loo Lin School of Medicine found that the high sensitivity and specificity of ultrasound-enabled accurate diagnoses of appendicitis even in cases where the appendix was only partially or not visible.

“This is a significant new finding, as scans with an incompletely or non-visualised appendix are often thought to be unhelpful in diagnosing or ruling out appendicitis,” says Principal Investigator, Dr Shireen Nah, Staff Physician, Department of Paediatric Surgery, KKH.

“As ultrasound is radiation-free, prioritising it as a first line of diagnostic imaging also allows us to minimise the risk of unnecessary radiation exposure for the child during the screening process,” Dr Nah adds.

Principal investigator, Dr Shireen Nah, Staff Physician, Department of Paediatric Surgery, KKH (centre), and her co-investigators Dr Tang Phua Hwee, Senior Consultant, Department of Diagnostic and Interventional Imaging, KKH (left), and Ms Sanjena Kumar, Medical Student, Yong Loo Lin School of Medicine, National University of Singapore.

In cases where the appendix could not be visualised on ultrasound or definitively categorised as normal or abnormal, the observation of secondary signs suggestive of inflammation in the right lower quadrant of the abdomen was greatly valuable in informing the interpretation of the scan, resulting in high diagnostic sensitivity (82.4%), specificity (99.3%), positive predictive value (99.3%) and negative predictive value (97.9%).

These secondary signs included hyperaemia, presence of thickened echogenic periappendiceal or intra-abdominal fat, extraluminal fluid collection, free fluid, presence of an appendicolith and non-compressibility of the appendix.

Excluding children who underwent ultrasound for other causes of abdominal pain, the use of supplementary computed tomography (CT) imaging to confirm a diagnosis of appendicitis was only necessary in 23 (3.5%) of 641 children who underwent ultrasound for suspected appendicitis.

“Altogether, these enabled us to maintain a low negative appendicectomy rate (2.2%) comparable to that of other leading medical centres, and a minimal risk of missed diagnosis, while preventing unnecessary surgical intervention and anaesthesia in children,” said Dr Nah.

Ultrasound imaging safer for children with suspected appendicitis

Appendicitis shares many of its common symptoms – such as abdominal pain, nausea with or without vomiting, loss of appetite and slight fever – with other causes of acute abdominal pain, such as genitourinary disorders and intussusception.

Furthermore, about 40 per cent of children who have appendicitis exhibit atypical or non-specific signs and symptoms. As a result, physical examination and clinical history notwithstanding, diagnostic imaging is necessary for an accurate diagnosis of appendicitis.

CT has traditionally been the imaging modality of choice for suspected appendicitis, due to its reliability in clearly visualising the appendix in a large number of patients, even those with a high body mass index. However, CT is associated with relatively high levels of radiation. 

Although the dosage is kept as low as possible in paediatric centres, the dose response relationship between ionising radiation exposure from paediatric CT scans and the risk of malignancy in children has been well-documented.

In contrast, ultrasound is non-invasive and radiation-free, making it a preferred alternative for the diagnostic imaging of children. It can be carried out repeatedly – even at the patient’s bedside if needed – with minimal harm to the patient.

“We are constantly exploring ways to minimise the risks our patients are exposed to and to help them achieve optimal treatment outcomes,” says co-investigator Dr Tang Phua Hwee, Senior Consultant, Department of Diagnostic and Interventional Imaging, KKH.

“The results of the study confirmed that ultrasound imaging can indeed be highly accurate in diagnosing appendicitis in children even when the appendix is not completely visualised, and that clinicians may safely use ultrasound results to supplement clinical assessment.”

“Moving forward, we are looking into faster, less invasive methods of diagnosing appendicitis and reviewing protocols to streamline the diagnosis process and increase accuracy. We are also extending research into alternatives for management of appendicitis, including non-operative treatment,” Dr Nah adds.