True regarding subphrenic abscess is

(B) It is most commonly seen following biliary tract surgery # Symptoms> A common history is that when some infective focus in the abdominal cavity has been dealt with, the condition of the patient improves temporarily, but after an interval of a few days or weeks, symptoms of toxaemia reappear.> The condition of the patient steadily, and often rapidly, deteriorates. Sweating, wasting and anorexia are present.> There is sometimes epigastric fullness and pain, or pain in the shoulder on the affected side, owing to irritation of sensory fibres in the phrenic nerve, referred along the descending branches of the cervical plexus.> Persistent hiccup may be a presenting symptom.# Signs> A swinging pyrexia is usually present, unless antibiotics or drugs (steroids) have interfered. If the abscess is anterior, abdominal examination will reveal some tenderness, rigidity or even a palpable swelling.> Sometimes the liver is displaced downwards, but more often it is fixed by adhesions. Examination of the chest is important, and in the majority of cases collapse of the lung or evidence of basal effusion or empyema is to be found.# Investigations> Blood count usually shows a leucocytosis.> A plain radiograph demonstrates the presence of gas or a pleural effusion. On screening, the diaphragm is often seen to be elevated (so-called 'tented' diaphragm) and its movements impaired.> Ultrasound or CT scanning is the investigation of choice and permits early detection of subphrenic collections.> Radiolabelled white cell scanning may occasionally prove helpful when other imaging techniques have failed.