Adrenal abscess in a 3-week-old neonate - a case report.

The authors present a case of a 6-year-old boy operated on in the 4th week of life because of adrenal abscess. The diagnosis of an adrenal abscess in the neonatal period is challenging due to its rare occurrence and non-specific signs. Adrenal abscesses can develop via two mechanisms: as a result of a hematogenic infection and a spread of bacteria to "normal" adrenal glands or, which is much more common, a complication of an adrenal hematoma. Early and accurate diagnosis is crucial for appropriate therapeutic management. Imaging, including ultrasound, can be problematic. The final diagnosis is frequently established on the basis of a histological examination of a surgical specimen.

Introduction

A neonatal adrenal abscess is a sporadic pathology and is rarely included in the differential diagnosis of adrenal tumors. It is suspected that, in most cases, it develops as a consequence of an adrenal hematoma which might be conductive to inflammation and the formation of an abscess. Non-specific signs can include fever and prolonged jaundice with elevated inflammatory markers. Early and appropriate diagnosis is crucial for appropriate therapeutic management and improvement of the child's condition. A delay in diagnosis can lead to sepsis and/or spread of inflammation to adjacent tissues and organs(.

The authors present a case of a 6-year-old boy operated on in the neonatal period because of right adrenal abscess. Attention is drawn to the clinical course and diagnostic difficulties in establishing the final diagnosis.

Case report

A boy born from the sixth gestation and fifth labor in the 40th week of pregnancy, as a result of a natural labor, was in a good overall condition, weighing 4,400 g with the body length of 60 cm. On day 3 after delivery, he developed jaundice that required phototherapy (maximum indirect bilirubin level 14.5 mg%). On day 8, the patient was transferred to the Pediatric Department of the Regional Hospital for the diagnosis of leukocytosis in CBC (28.9 thousand /mm3), which was conducted because of the boy's unrest while changing diapers. There were no other signs. Tests performed in the hospital revealed increased inflammatory markers (Tab. 1). A chest X-ray examination revealed interstitial inflammatory densities in both lungs. Urine culture demonstrated the presence of Escherichia coli, and blood culture showed methicillin-sensitive Staphylococcus aureus (MSSA). The cerebrospinal fluid was normal. Despite antibiotic therapy (amoxicillin with clavulanic acid, amikacin, ceftriaxone) and normal blood culture, high leukocytosis still persisted (22.8–23.8 thousand /mm3), and C-reactive protein (CRP) increased from 41.4 mg/dl to 105.9 mg/dl. An abdominal ultrasound scan revealed a cyst-like, cystic-solid lesion (5 × 3 cm) in the upper pole of the right kidney. A subsequent US examination, conducted 3 days later, revealed a visible level of dense fluid within the cyst (Fig. 1).

Tab. 1

Results of laboratory tests

Type of examination	Regional Hospital	Department of Surgery, Medical University of Warsaw
		before surgery	after surgery
Leukocytosis (×103/mm)	27; 22.8; 23.8	26; 25.1	17.3; 10.4
CRP (mg/dl)	41.6; 61.4; 105.8	17.1; 16.5	11.8; 2.7

Fig. 1

Pre-operative abdominal US: a cyst-like, cystic-solid lesion (5 × 3 cm) in the upper pole of the right kidney with a visible level of dense fluid within the cyst

The boy was transferred to the Department of Pediatric Surgery and Urology of the Medical University of Warsaw in the third week of life with a diagnosis of right renal abscess, sepsis and a suspicion of a congenital urinary tract defect. Upon admission, the child was in a good condition, without fever and without any palpable tumor in the abdominal cavity. Laboratory tests revealed leukocytosis and elevated CRP (Tab. 1). The creatinine level, urinalysis and urine culture were normal. A generalized infection was ruled out. An abdominal US scan revealed a cystic lesion with a diameter of 6 cm, probably representing a hematoma of the right adrenal gland. In order to confirm the nature of the lesion, contrast-enhanced computed tomography (CT) was conducted (Fig. 2). Based on imaging findings, a urinary tract defect was ruled out, and a tumor of the right adrenal gland, in the form of an enormous cyst with thick walls, was diagnosed. It probably had an inflammatory character (increased inflammatory markers) – adrenal abscess. Prior to the scheduled surgical procedure, the boy was consulted by an oncologist and endocrinologist. Neuron specific enolase (NSE – 30.16 µg/l; norm to 18.3 µg/l) as well as catecholamines in 24 h urine collection and cortisol (normal results) were determined.

Fig. 2

Pre-operative abdominal CT: in the right adrenal gland, an encapsulated lesion with the size of 53 × 43 × 42 mm and density of 26 HU with no enhancement upon contrast agent administration; the lesion moves and rotates the right kidney; the capsule of 50 HU is enhanced upon contrast agent administration to 150 HU

The boy was operated on in the 4th week of life. The tumor of the right adrenal gland (with the size of 8 × 6 × 4 cm) was removed. Macroscopically, it presented features of an inflammatory tumor – an abscess. The tumor was ingrown in the hepatic hilum and fused with the right dome of the diaphragm; it pushed and rotated the right kidney (Fig. 3). Histology confirmed right adrenal abscess (Fig. 4). The abscess culture revealed MSSA. The postoperative period was insignificant, with no fever. Ceftazidime and netreomycin were used protectively. Inflammatory markers gradually decreased (Tab. 1). A direct postoperative US examination of the abdominal cavity revealed both kidneys of normal echogenicity, without pelvicalyceal system dilatation. The left kidney (43 mm long) was in its typical position, and the right one (41 mm long) was located lower and more medially. Another US scan conducted 1.5 months after the procedure failed to present the right kidney. Dynamic renal scintigraphy revealed no tracer accumulation in the anatomical position of the right kidney. The left kidney of normal position was relatively large. It efficiently accumulated and excreted the tracer. The pelvicalyceal system of the left kidney and the left ureter were slightly dilated (Fig. 5). Due to the difficulties in visualizing the right kidney in consecutive US scans, the boy underwent a CT scan at the age of 4 months. It revealed an area corresponding to a small cirrhotic kidney in the typical position of the right kidney. The left kidney and the left adrenal gland were normal (Fig. 6). Subsequent US examinations revealed a small hyperechoic structure with the size of <2 cm at the site of the right kidney (Fig. 7).

Fig. 3

Intraoperative presentation of right adrenal abscess

Fig. 4

Removed right adrenal abscess

Fig. 5

Dynamic renal scintigraphy: no tracer accumulation in the anatomical position of the right kidney; the left kidney with normal position effectively accumulates and excretes the tracer

Fig. 6

Post-operative abdominal CT: at the site of the right kidney, there is a structure of approximately 9 × 15 mm with little excretory function; the left kidney and adrenal gland are normal

Fig. 7

Postoperative abdominal US (6 months after the procedure): a slight hyperechoic structure (less than 2 cm long) at the site of the right kidney

The boy remains under constant nephrological care. Renal function parameters are regularly monitored and remain normal. US shows the normal left adrenal gland and kidney; the pelvicalyceal system and ureter are not dilated. Dynamic scintigraphy confirms normal secretory and excretory function of the left kidney. The boy was also under endocrinological care. The function of the right adrenal gland was normal with no signs of insufficiency.

Discussion

An adrenal abscess in a neonate is a sporadic clinical problem (fewer than 50 case reports(). It is suspected to develop mainly because of a superinfection and inflammation within the site of previously extravasated blood to the adrenal gland, which is favored by the specific structure of this organ(. In neonates, the adrenal glands are relatively large, because of the presence of the persistent fetal cortex, and well-vascularized. The broad availability of ultrasonography on neonatal units enables adrenal hematomas to be detected more and more frequently. It is estimated that they develop in 1.7–2.1 per 1,000 neonates. They are statistically more frequent in boys born at term with significant perinatal history (birth trauma, perinatal hypoxia, intrauterine infection, coagulation disorders)(. Because of different anatomical conditions, hemorrhage occurs in the right adrenal grand in approximately 70% of cases. The right gland is located between the liver and spine which may compress it. Moreover, the direct connection of the right adrenal vein with the inferior vena cava and coexisting risk factors are conductive to disorders in blood outflow from the gland and to blood extravasation. This pathology is bilateral in only 10–15% of cases(.

More rarely, adrenal abscesses develop as a result of a hematogenic infection and spread of bacteria to “normal” adrenal glands, which is observed in neonates with sepsis(. In the case presented above, both mechanisms can be considered. Although no risk factors predisposing to adrenal hemorrhage were found, imaging examinations and the right side of the lesion indicate that inflammation probably developed due to a hematoma. The lesion described in the first ultrasound examination (cyst-like, solid-cystic) can correspond to a hematoma during resorption. This would suggest that hemorrhage to the adrenal gland occurred a dozen or so days before (fresh extravasated blood in the adrenal gland is manifested as a solid lesion of high echogenicity). It seems that bacteremia and destruction of the adjacent kidney could be consequences of the abscess. However, it cannot be excluded that the generalized infection was the cause of bacterial spread to the adrenal gland and the development of the abscess. Staphylococcus aureus was found in both abscess and blood culture tests. According to the literature, next to Escherichia coli, these bacteria are the most common pathogens of adrenal abscesses. There have been single cases of a neonatal adrenal abscess caused by group B Streptococcus, Bacteroides fragilis, Echovirus and Herpes simplex(.

The clinical signs that accompany adrenal abscesses are non-specific. They usually include: fever, irritation, difficulty with feeding, no body mass increase and a tumor in the abdominal cavity(. In the case presented above, the only alarming sign was different behavior of the child and irritation. Laboratory tests demonstrated elevated inflammatory markers which did not normalize despite antibiotic therapy that lasted for a dozen or so days. The first abdominal US scan revealed a lesion suggesting a renal abscess. A diagnosis of an adrenal abscess was established in the third week of life based on imaging and laboratory examinations. This diagnosis was confirmed upon a histological examination of the removed tumor.

The differential diagnosis of neonatal adrenal tumors must involve Wilm's tumor, neuroblastoma and a congenital urinary tract defect in the form of complete pelvicalyceal system duplication with dilatation of the upper segment and hydronephrosis(. Ultrasound images of adrenal hemorrhage and a hemorrhagic form of neuroblastoma can be identical. The presence of calcifications in the first images and vessels in the power Doppler examination as well as the lack of the evolution of the lesion in subsequent scans indicate the neoplastic nature of the tumor(. Determining the levels of neuron specific enolase in the serum as well as catecholamine and its metabolites in 24h urine collection can be helpful in establishing the diagnosis(. In our patient, the level of catecholamines was normal, and the level of NSE was slightly elevated. Neuron specific enolase is a cancer marker in the neuroendocrine system. Its concentration is also elevated in diseases associated with non-neoplastic neuronal damage, such as: stroke, head trauma, Alzheimer's disease and following an epileptic attack. Apart from the cells of the central and peripheral nervous system and neuroendocrine cells, this enzyme can be found in erythrocytes and platelets. Conditions with hemolysis can also be a cause of increased neuron specific enolase in the serum(. Perhaps, red blood cells were destroyed upon extravasation which might have resulted in falsely increased NSE values.

Since adrenal abscesses in neonates are rare, one uniform management has not been established. In most cases, neonates are operated on with an initial diagnosis of adrenal tumor(. The patient presented above also underwent laparotomy and had the adrenal tumor removed. The literature also mentions single cases of percutaneous ultrasound-guided abscess drainage with good effects(.

Conclusion

An ultrasound scan is a valuable examination used for the detection and monitoring of adrenal pathologies. In the case of a lesion that evokes doubts, additional imaging examinations, such as CT and MRI, may be needed. The presence of non-specific signs of infection and elevated inflammatory markers in a neonate with an adrenal hematoma and significant perinatal history should raise a suspicion of an abscess. A rapid and accurate diagnosis is crucial for appropriate treatment to prevent a generalized infection and destruction of adjacent organs.