USG is the imaging of first choice as it is quick, safe, cheap, and accurate in picking up a liver lesion. Appearances of an abscess may be a round or an oval lesion which is usually hypoechoic but may have heterogenous echotexture. A solid or heterogenous lesion often evolves into a hypoechoic lesion on subsequent examination [5]. Majority of the abscess have a well-defined wall which may be thin or irregular. However USG may miss very small abscesses or abscesses lying in areas of liver difficult to examine when patient co­-operation is poor. CECT is more sensitive in detecting even small abscesses anywhere in liver. Yet it is inconvenient with risk of contrast nephropathy being always there. A hypodense lesion with low attenuation areas and an enhancing rim is a classical CECT image. Small hypoechoic lesions in cluster may suggest a beginning of process of coalescence into a single large abscess later. Liver abscesses on MRI appear hypointense on T1 weighted and hyperintense in T2 weighted sequences. On gadolinium enhanced sequences, there is early and continued enhancement of wall which persists on delayed images. There is increased peri-abscess tissue enhancement in immediate post-gadolinium images. With all the inconveniences of time and cost attached to MRI, it is at its best of same capability as CECT. Of all imaging modalities, USG is best for follow up, although it is not routinely necessary. The abscess cavity takes many months to finally resolve and lags behind clinical resolution by months [6].

In lung abscesses we found that fever and cough were the most common presenting symptoms. We found that Staphylococcus and Streptococcus were the most common single pathogens, which correlates with previously reported studies [1].

Imaging is very important in definitive diagnosis of pulmonary abscess. The diagnosis is made on the basis of pulmonary X-ray and/or thoracic CT taken upon suspicion. The presence of air-fluid level in parenchyma is typically seen on the pulmonary X- ray. Among 20% of abscess cases, the pulmonary X-ray may not lead to a definitive diagnosis in the initial stage [7].

A pulmonary abscess is generally singular and it is seen in a single lobe. However, they may be multiple or localized in different lobes among patients with aspiration pneumonia, necrotizing pneumonia and especially immune deficiency [8]. The abscesses occurring as a result of aspiration are seen more often in the right lung than the left lung since the right main bronchus has a wider angle with trachea as compared to the left one. Pulmonary abscess is mostly seen in the higher lobe segment of the right lung or in the lower lobe superior segment [8]. If aspiration took place when the patient was in supine position, the abscess develops most frequently in this segment since the lower lobe superior segment is in the lowest point in this position.

Retropharyngeal abscess is most common­ly due to rupture of a suppurative retropharyngeal node into the retropharyngeal space and is contained only by the fascia surrounding the retropharyngeal space. Oth­er less common causes of a retropharyngeal abscess are spread of infection from contig­uous spaces across the fascial boundaries or direct inoculation from penetrating trau­ma. Before infection evolves into a walled abscess, it is known as retropharyn­geal cellulitis or phlegmon. This condition can be difficult to differentiate from retro­pharyngeal edema [4]. The typical clinical pre­sentation of retropharyngeal abscess is acute to subacute onset of neck pain, dysphagia or odynophagia, and a low­grade fever.

Retropharyngeal abscesses have an oval or rounded configura­tion; cause moderate­ to ­marked mass effect and can pro­duce anterior displacement of the pharynx and flattening of prevertebral muscles. They usually have a thick enhanc­ing wall.

The mortality rate for retropharyngeal ab­scess is less than 1%  and has declined in the last 50 years because of the availability of antibiotics and early diagnosis with CT/MRI. The most urgent complication is airway compres­sion from mass effect on the larynx and phar­ynx. Airway compromise is suggested in up to 3% of patients by the clinical symptom of stri­dor [9].

Muscle abscess typically starts as a localized infection of muscle, beginning with pain and swelling. The diagnosis is often overlooked or delayed because most physicians are not familiar with the entity. Local signs of inflammation, fever, leukocytosis and elevated erythrocyte sedimentation rate are common features [10]. The involved muscles may eventually develop a firm, wooden texture on palpation. Later, as an abscess forms the muscle becomes fluctuant. Any skeletal muscle can be involved, but large muscles of the lower extremities are commonly affected. Blood cultures are positive in about 30% of patients [11].

Most patients do well with appropriate intravenous antibiotics if detected early and a fatal outcome is rare. Ultrasonography is particularly useful to monitor progression from pre-suppurative phase to suppurative phase, and also to guide the area of drain. Imaging spectrum ranges from early stage of Pyomyositis to frank muscle abscess formation. On the T1-weighted MR images, pyomyositis is suggested by a high-signal-intensity rim. It is probably produced by paramagnetic material such as methaemoglobin from subacute haemorrhage, bacterial or macrophage sequestration of iron, and/or free radicals that shorten the T1 of tissue in the periphery [12] MRI also proved valuable in differentiation of the intramuscular inflammatory infiltrate of early `invasive' phase of pyomyositis (with focal areas of increased intensity on T2 weighted images) from muscle abscesses of later stages (with its rim of increased signal intensity around the abscesses on T1-weighted images). [12] Muscle abscess gives typical appearance on T2 hyperintense lesion with peripheral contrast enhancement and diffusion restriction.

There are several limitations of this study, which include its retrospective nature and it being limited to a single center.

High suspicious index is needed in infants for diagnosing abscesses. Radiologists should be aware of its varied imaging spectrum.