Introduction 1 Case report An otherwise healthy 3.5-year-old boy was brought in with severe oral bleeding. Nine days prior to the presentation he had undergone an adenotonsillectomy for chronic adenotonsillitis in another hospital. The tonsils had been removed with cold dissection and sutures had been placed in both tonsil areas. The procedure and the immediate postoperative period went uncomplicated. On the fifth postoperative day he had been admitted for a one-night observation because of haemorrhage from the mouth. During the admission no active bleeding was observed and his haemoglobin level of 4.9 mmol/l (normal values: 6.5–8.4 mmol/l) was treated conservatively. The second postoperative bleeding started 9 days postoperatively, late at night when the patient was lying in bed. There were no provoking events. The bleeding lasted around 10 min but had already stopped at arrival in our emergency room. We saw a pale and restless boy. Intra-oral examination in general anaesthesia showed lacerated pharyngeal muscles in the left tonsillar fossa and a loose suture was removed. The right tonsillar fossa revealed diffuse bleeding from the pharyngeal muscles without pulsating masses. The nasopharynx and tongue base showed no abnormalities. The haemoglobin was increased from 2.9 to 8.2 mmol/l by transfusion with two units of packed red blood cells. The coagulation values were within the normal range. The postoperative period was uncomplicated, so he was discharged after 5 days, 15 days after the primary intervention, with dietary advices. One day later the boy arrived by ambulance with heavy bleeding from the mouth. He was pale, shivering and drowsy. Again, the severe bleeding started without a provoking moment and persisted for about 15 min. Immediately, after arrival at our emergency department, he was re-explored intra-orally under general anaesthetics. We saw a bluish, pulsating mass of 5 by 12 mm low in the right tonsillar fossa without active bleeding. The faucial pillars on the right side were approximated without tearing the mucosa or induration of the aneurysm. However, during extubation a massive bleeding occurred. The boy was re-intubated, and with digital oral pressure during 15 min haemostasis was achieved. 1 2 3 Fig. 1 Pseudoaneurysm of the right lingual artery seen from right-anterior side (3D-surface rendering)  Fig. 2 Arteriography of pseudoaneursym of the right lingual artery seen from right-anterior side  Fig. 3 2  The boy was extubated without any bleeding and 4 days after the embolisation he was discharged in a good clinical condition. At a follow-up examination, he did not report any intra-oral or neurological abnormalities. Discussion True aneurysms develop through congenital or acquired weakness of all three layers of the vascular wall. False or pseudoaneurysms may arise due to localised arterial wall laceration caused by blunt or penetrating trauma. The intima or adventitia layer of the vessel wall is dissected, which creates a periarterial haematoma. Pseudoaneurysms after tonsillectomy may be triggered by blunt or direct trauma during dissection or due to placing ligation sutures. 2 3 4 5 6 It is striking that the above-mentioned cases of posttonsillectomy pseudoaneurysms concerned children under the age of 10 years. No cases of posttonsillectomy haemorrhage due to pseudoaneurysms in adults have been reported. This suggestive higher incidence of pseudoaneurysms in children might result from the smaller anatomy and thinner pharyngeal muscles, and a subsequent higher risk of damaging the large vessels. 5 7 Conclusion Pseudoaneurysms are life-threatening and should be considered in severe posttonsillectomy haemorrhage. Pseudoaneurysms do not always present as intra-oral or cervical pulsating masses, and can develop gradually. If the technique and technical crew are available, interventional arteriography is strongly recommended in severe posttonsillectomy haemorrhage. It is diagnostic and therapeutic at the same time and more selective than surgical ligation.