General Pediatric Renal Replacement Options

The glomerular filtration rate (GFR) is equal to the sum of the filtration rates in all of the functioning nephrons; therefore, estimating the GFR gives a rough measure of the number of functioning nephrons.

Initial calculations utilized to estimate GFR in children relied heavily upon serum creatinine concentration. ^{[1, 2]}  Given the well-recognized influences on creatinine (ie, muscle mass) and the introduction of cystatin C as a reliable marker of renal function, a newer equation has since emerged. The “CKiD under 25” (also known as “U25”) is the most recently validated GFR estimating equation, which utilizes both age- and sex-specific constants “K” and incorporates creatinine as well as cystatin C. ^[3]

The global nonprofit foundation Kidney Disease: Improving Global Outcomes (KDIGO) has stratified renal function in chronic kidney disease (CKD) based on the GFR. ^[4]  See Table 1 below.

Table 1. CKD Stage (Open Table in a new window)

*The classification in Table 1 applies to children aged 2 years or older, because the GFR only becomes equivalent to that of adults between 1 and 2 years of age. ^[4]

The natural history of kidney disease is variable and unpredictable, but generally there is continued progression of CKD, which is defined by a declining GFR. ^{[4, 5]}  End-stage kidney disease (ESKD) refers to a glomerular filtration rate less than 15 mL/min/1.73 m².

When considering the etiologies of pediatric ESKD, if stratified by age, congenital anomalies of the kidney and urinary tract (CAKUT) predominate as the cause of ESKD in children younger than 1 year of age. ^[6]  As children age, the causes of ESKD shift. The incidence of glomerulonephritis (GN) rises, overtaking CAKUT after the age of 6 years, with focal segmental glomerulosclerosis (FSGS) and lupus nephritis predominating as the causes of primary and secondary GN, respectively. ^[7]  If, however, all other variables are discounted, the most prevalent cause of pediatric ESKD is FSGS. ^[8]

Renal replacement therapy (RRT) encompasses both dialysis and transplantation. Dialysis will be the primary focus here. When considering dialysis, the two main modalities used in pediatrics are in-center hemodialysis and peritoneal dialysis (PD). Home hemodialysis may be used as well but with much lower frequency; therefore, it will not be expanded upon in this discussion.

Modality choice and associated complications

Many factors enter into the choice of an appropriate dialysis modality. First and foremost, given the immense responsibility that rests upon the shoulders of caregivers, parental preference must be taken into consideration to provide the best care for both the child and the family.

Patient-specific considerations that weigh into the choice of a modality include age and size. PD tends to be better tolerated and is therefore preferred for infants and small children. In those younger than the age of 1 year, PD is utilized over 90% of the time, whereas in those aged 1-5 years, it is used just over 50% of the time. In patients aged older than 6 years, hemodialysis becomes the favored modality. ^[7]  Additional considerations include distance from a long-term dialysis facility (potentially precluding travel to and from a hemodialysis unit), as well as consistent support from a caregiver who is able to provide home-based dialysis.

PD affords the advantage of therapy performed at home and at night, which allows for more routine day-to-day activities, as well as uninterrupted school attendance. 

PD is contraindicated in patients in whom the integrity of the peritoneum has been impaired (eg, those with gastroschisis, omphalocele, bladder exstrophy, or diaphragmatic hernia) or in those with an extraperitoneal communication (ie, a diaphragmatic hernia). The presence of a colostomy, gastrostomy, ureterostomy, or Mitrofanoff channel does not preclude the ability to perform PD. ^[9]

Complications of PD are both infectious (exit site, tunnel, and peritonitis) and non-infectious (catheter malfunction, extra-peritoneal communication [pleural-peritoneal or pericardial fistula]). ^{[9, 10]}

After the age of 6 years, hemodialysis becomes the preferred modality. ^[7]  Hemodialysis requires travel to and from a pediatric dialysis facility or an adult facility skilled in caring for pediatric patients. It removes some of the burden on caregivers associated with PD, which can help relieve the stress placed on families.

Hemodialysis necessitates functional central access. Risks include infectious complications (exit site, tunnel, and bloodstream) ^[11]  as well as mechanical complications of the line. Additionally, given the need for anticoagulation, bleeding is a risk as well.

Again, whether providing in-home PD or traveling for in-center hemodialysis, a significant responsibility is placed upon caregivers, most notably during a child’s early years. It cannot be overstated that this must be factored into the modality choice to provide the best care for the entire family.

Access

Patient size and comorbid conditions influence access considerations in pediatrics for both PD and hemodialysis, which require surgical expertise for successful outcomes. Many children who need PD have congenital anomalies that mandate surgical access via the abdomen outside of their catheter (ie, a colostomy or Mitrofanoff procedure). This necessitates thoughtful PD catheter placement and strict peri-catheter care to minimize the risk of infection. ^{[6, 7]}

Hemodialysis access also necessitates a distinct approach in pediatric patients. The “Fistula First” approach has become increasingly popular for well-described reasons, including improved long-term access survival and adequacy, as well as decreased infections and hospitalizations. However, the early, preferential creation of a fistula has lagged behind in pediatrics for numerous reasons. Surgical creation, troubleshooting, and maintenance of a fistula require surgical and nursing expertise, which may be lacking in certain centers. Small vessel size may also play a role. There is an overall presumption that children will receive a transplant “soon,” negating the need for fistula creation.

Finally, patients and families may have concerns regarding the cosmetic impact of a fistula or the perceived pain with cannulation. It behooves healthcare providers to be aware of these barriers, which result in higher rates of long-term central venous catheter (CVC) use. It is important to be cognizant of the inherent complications arising from CVC use and take a preemptive approach to the prevention of these complications. ^{[8, 12]}

When GFR approaches less than 15 mL/min/1.73 m², children may need dialysis; however, this is not an absolute indication. Irrespective of GFR, if a child is asymptomatic and is being monitored closely, dialysis can be delayed. Ultimately, the decision to initiate is based on a constellation of signs and symptoms refractory to medical therapy, including the following:

• Fluid overload
• Uremic symptoms (eg, fatigue, malaise, anorexia, weight loss, nausea, vomiting, poor caloric intake)
• Metabolic abnormalities (eg, hyperkalemia, acidosis, hyperphosphatemia, hypocalcemia)

CKD is stratified according to GFR.

ESKD refers to a GFR of < 15 mL/min/1.73 m².

RRT options include both dialysis and transplantation.

CAKUT is the most common cause of ESKD in pediatric patients when the causes are stratified by age.