The role of pediatric chest US in the diagnosis of hydrothorax complicating peritoneal dialysis

2018-04-04 08:03:27

Category: Pediatric radiology, Region: Thorax-Lungs, Plane: Other

ABSTRACT Hydrothorax is an uncommon but well-recognized complication of pediatric peritoneal dialysis (PD). Experience with pediatric patients on PD who develop hydrothorax is limited and diagnostic procedures are still debated. We describe the case of 2-year-old female, on automated peritoneal dialysis (APD) for end-stage renal disease (ESRD), who developed a right-sided hydrothorax, to discuss the diagnostic role of lung ultrasonography (US) in detecting pleural complications in children treated by PD. Lung US enables the detection of pleural complications like hydrothorax, in children with ESRD treated by PD. CASE REPORT A 2-year-old female with ESRD due to congenital nephrotic syndrome treated by APD presented to monthly peritoneal dialysis ambulatory visit with polypnea, dyspnea and reduced breath sounds and percussion dullness on the right side, with oxygen saturation of 88% on capillary hemogasanalysis. The patient started renal replacement therapy (RRT) with APD since six months with the following scheme therapy: a total volume exchange of 2000 mL, eight cycles, 240 mL for each charge, duration of treatment nine hours. Thereafter, the APD prescription was modified with mild increase of charge at 300 mL per cycle (less than 40 ml/kg), well toleraded by the patient. The recent clinical history showed fever two weeks before, treated with oral antibiotics for documented Streptococcical pharyngitis. In the days before the visit, she presented a mild increase of diuresis and reduced ultrafiltration. Test performance characteristics for the ability of lung US to diagnose pleural complications in this child were determined using chest X-rays as a reference standard. Lung US examinations were performed by the same experienced paediatric radiologist, using a 7.5 MHz linear and convex probe and both trans-thoracic and trans-abdominal approaches. The transthoracic US approach included examination in supin and both lateral decubitus positions of the anterior, lateral and posterior lung areas in caudo-cranial direction. The trans-abdominal US included the trans-hepatic and trans-splenic approach in supin position to examine both lung bases3. For the evaluation of pleural effusion, was used vector or convex transducer with a larger field of view to quantify the effusion. For the examination of the diaphragms, was used a tight convex transducer in the subxiphoid area to simultaneously view the right and the left hemidiaphragms excursion. A linear transducer is best for evaluation of each hemidiaphgram contour and muscle. Both chest X-rays and US showed a pleural effusion on the right side (FIG. 1-2) Clinical signs and syntoms, but also laboratory data were negative for other causes of hydrothorax, so a pleuro-peritoneal communication was suspected, PD was withheld, and the patient transitioned to temporary hemodialysis. After 5 weeks, the chest X-ray and the US did not identify any pleural effusion (FIG 3-4). The APD prescription was modified with reduced charge volume at 25 ml/kg and APD recommenced without evidence of hydrothorax recurrence. Comparisons showed a complete match between chest X-rays and lung US findings. DISCUSSION AND CONCLUSION Ambulatory peritoneal dialysis (APD) is frequently used in the pediatric age group for acute kidney failure or chronic ESRD. Most pediatric patients tolerate well this therapy with few complications. A variable percentage of children, however, may develop massive unilateral hydrothorax. A recent survey from the European Paediatric Dialysis Working Group reported an incidence of 0.66% in a cohort of PD patients during 10 year of observation.3 This major complication usually results in the discontinuation of peritoneal dialysis and the start of hemodialysis.4 Occult diaphragmatic defects account for most adult and pediatric patients who develop this complication. 5 A high index of suspicion is required to make an early diagnosis, since it is a serious diagnosis that may require urgent treatment. Although there are no clearly defined diagnostic tests for this complication, pleural effusion usually is diagnosed on chest X-ray and confirmed on ultrasonography in pediatric patients. No standard practice for this condition exists, and experience with investigations and management is limited. The therapeutic options are variable and range from conservative management with reduction or stopping of PD to active treatment with pleurodesis or thoracotomy to repair the diaphragmatic eventration. 3 Outcomes can be variable and some authors report the necessity to stop PD definitely for recurrence of hydrothorax. 6 In our patients it was sufficient to stop PD treatment for few weeks. This case report demonstrates a classical presentation and course of hydrothorax, underlying its relevance for all clinicians encountering patients receiving PD. The continuous balancing between the potential harmful effects of diagnostic procedures based on X-rays and their potential benefits is especially highlighted in pediatric radiology. Given the possibility of evaluating pleural lesions, lung US in children has been recognized as a potentially useful diagnostic method. This is supported by the fact that children have a thinner thoracic wall, and smaller width of the thorax and lung volume, which enables a better image quality and visualization of almost the entire surface of the lungs compared to the adult population. Also, the relative simplicity of mastering the basic lung US patterns is of great importance. 7 US imaging is very sensitive for the evaluation of pleural effusion and can detect effusion as less as 3-5 mL. It is often used in the evaluation of critically ill children when upright or decubitus chest radiographs cannot be performed. In the setting of an observation of “white” hemithorax on chest radiograph, supine and decubitus views may not helpful in differentiating between pleural fluid, lung consolidation, or atelectasis. US can also differentiate between simple non-loculated effusion and complicated effusion and help to direct management. Nevertheless, experience may play an important role in lung US examinations. An experienced pediatric radiologist can perform this examination faster, which is extremely important in such a vulnerable population as children are. So the advantages of lung US are numerous: it needs a very short training either to perform the exam or to interpret the images, allows a bedside evaluation of the patient without exposure to ionized radiation and therefore can be repeated several times without risk. 8 Our case report demonstrates the usefulness of lung US in diagnosis and follow-up of hydrothorax in PD pediatric patients. However our case report has several limitations. Chest X-rays is an imperfect reference but is still a practical and standard diagnostic test for this case. CT of the chest would be a more accurate reference standard, particularly for pleural effusions that were detected by US but not by chest X-rays, but obtaining chest CT in our case was not practical and is not standard of care. 8 Both diagnostic modalities have been evaluated by the same investigator, which makes bias difficult to exclude entirely. The investigator was the only experienced pediatric radiologist in the field of lung US. Also, it was not possible to conduct a blinded, independent survey of these examinations in this very demanding and time-consuming study due to a small number of pediatric radiologists in our hospital, which is the only children’s hospital in this region. 7 Since US scans were performed by a single experienced operator, it is reasonable to hypothesize that similar results might not be immediately achieved by less experienced operators.3 In conclusion, lung US enables the detection of pleural complications (hydrothorax in our case) in children with ESRD treated by PD. We believe that lung US in combination with clinical parameters has the potential to reduce the number of Chest X-rays in these conditions. On the basis of our limitations, we think it is necessary to conduct more extensive, preferably multicentric diagnostic studies. These studies could confirm our findings and give quantitative measures of sensitivity and specificity about diagnostic procedures. From these results authors could provide specific guidelines for the use of lung US in hydrothorax complicating PD in children. TEACHING POINT Lung US enables the detection of pleural complications in children with ESRD treated by PD. Lung US in combination with clinical parameters has the potential to reduce the number of Chest X-rays in these conditions. REFERENCES 1. Complications of peritoneal dialysis: diagnosis and management. Holley JL, Piraino BM. Semin Dial. 1990 Oct;3(4):245-248. doi: 10.1111/j.1525-139X.1990.tb00057.x. 2. Pathogenesis and management of hydrothorax complicating peritoneal dialysis. Szeto CC, Chow KM. Curr Opin Pulm Med. 2004 Jul;10(4):315-319. 3. Pleuro-peritoneal or pericardioperitoneal leak in children on chronic peritoneal dialysis-a survey from the European Paediatric Dialysis Working Group. Dufek S, Holtta T, Fischbach M, et al; European Paediatric Dialysis Working Group. Pediatr Nephrol. 2015 Nov;30(11):2021-2027. doi: 10.1007/ s00467-015-3137-z. 4. 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