The urachus is a fibrous tubular structure that begins narrowing during the fourth and fifth months of gestation. It extends from the anterior bladder wall toward the umbilicus, as the median umbilical ligament, within the space between the peritoneum and transversalis fascia [1]. Urachal anomalies may be present in 2% of the general population and they are classified into four anatomic categories: patent urachus (50%), umbilical-urachal sinus (15%), urachal diverticulum (3 to 5%) and urachal cyst (30%). Usually, urachal anomalies remain asymptomatic unless there are complications such as infection, lithiasis and malignant degeneration. In general, symptoms include fever, lower abdominal pain and palpable suprapubic mass, with or without systemic or laboratory evidence of an infectious process [2]. The diagnosis of these anomalies requires ultrasonography, computed tomography and magnetic resonance imaging. The traditional treatment of an infected urachal cyst is composed of a two-stage approach: an incision and then drainage of the infected cyst followed by secondary excision [3].

In this paper, we describe a case of spontaneous regression of urachal cyst, occurring in a child after incision and drainage only, and we analyse the diagnosis and treatment of this rare disorder. Until now, only one case of infected urachal cyst presenting as fever of unknown origin has been described in the literature [4]. This report is important for paediatricians, who should consider the possibility that a fever of unknown origin can be caused by an urachal cyst, and for surgeons and urologists, in order to consider a conservative treatment of this congenital defect.

Urachal cyst is a congenital birth defect characterised by a sinus remaining from the allantois during embryogenesis and is the most common urachal anomaly in the paediatric population. Robert et al. noted a physiological regression of urachal anomalies with age. Because urachal remnant diseases are uncommon and manifest with non-specific abdominal or urinary signs and symptoms, surgeons and urologists should be acquainted with the treatment of these rare anomalies, especially in paediatric populations [5]. Knowledge of embryology and anatomy and having a high degree of suspicion are therefore very important to define a correct diagnosis. Although the guidelines reported in the latest edition of Grosfeld’s Paediatric Surgery recommend a surgical treatment of infected urachal cysts, spontaneous resolution without the need for surgical excision has been reported [6]. Another surgical option of the management of infected urachal cysts suggests an initial incision and drainage, followed by a later excision of the urachal remnant [7].

In our case we did not perform the second-look surgery. The urachal cyst was completely reabsorbed after the incision and the drainage and, 6 years later, remained absent on subsequent imaging studies. A histological examination demonstrated that there was no mucosa and it did not reveal any sign of malignancy. Even though this histological study regarded only a part of the cyst, we suppose that probably the purulent inflammation destroyed the mucosa lining the cavity of the cyst, thus excluding the possibility of a neoplastic degeneration. Although many surgeons recommend that urachal anomalies are removed to avoid potential malignant transformation later in life, no association has been established between urachal anomalies and urachal carcinoma [8]. Therefore, in our opinion, it seems imprudent to excise urachal remnants in infancy or childhood with the purpose of preventing a risk of developing cancer later in life.

In the literature there is only one study on fever of unknown origin caused by infected urachal cysts [4] and there is very little on treatment with incision and drainage only. In children who have a fever of unknown origin for more than 3 weeks and/or abdominal pain without a specific cause, the possibility of an urachal cyst should therefore be considered and a period of surveillance may be necessary and reasonable before surgery is performed. In our case, for the treatment of an infected urachal cyst, we preferred the laparoscopic approach instead of the percutaneous one. The laparoscopic approach allows a more complete diagnostic balance in which the relation of the cyst with respect to the bladder is better defined, and it allows exploration of the abdominal cavity and its organs. In our opinion, the laparoscopic approach represents a strong treatment of infection. In fact, this approach allows a large incision of the cyst with a complete emptying of purulent material, a better cleansing of the residual cavity and the possibility to take biopsy samples.

Certainly, we do not draw conclusions with a single case, but our experience in surgery, and in particular in laparoscopic techniques [9], has given us convincing reasons to confirm that the performance of the incision and drainage of the infected urachal cyst, through a minimally invasive laparoscopic approach, is a simple and safe procedure. It assures a complete recovery avoiding potential surgical complications related to the total excision of the urachal cyst.

In conclusion, we report a rare case of fever of unknown origin caused by an infected urachal cyst, which was successfully treated with incision and drainage only. Clinical presentation is non-specific; therefore, a high index of suspicion is required in order to make the diagnosis. This is a rare pathology and, despite the guidelines recommending surgical treatment, we chose a conservative approach. Diagnostic imaging studies performed during the follow-up showed the complete resolution of the cyst. In the light of these data, we emphasise the educational merits of this original case report considering also that very little is present in the literature on this topic.

Written informed consent was obtained from the patient, now adult, for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.