A Rough Road Ahead

Last month, a baby came into the world without kidneys. This is not generally a topic for news coverage (it happens more often than you think), but this girl’s mother is U.S. Rep. Jaime Herrera Beutler. Despite prenatal warnings about the grave prognosis, the Representative chose to continue her pregnancy with periodic intrauterine saline infusions. The fluid substitutes for fetal urine in utero, allowing better lung development and preventing the deformities induced by uterine compression in the absence of amniotic fluid.* This procedure has been used since the 1990s with variable success.

Abigail, the infant, was born prematurely, at 28 weeks of gestation and a weight of 2 lb 2 oz. A baby this premature has a hard road ahead of her, even if everything else is normal. Having no kidneys just makes things that more complicated.

Two studies examined single-center prognosis for infants on chronic dialysis, generally peritoneal dialysis (treatment the Beutler child is undergoing). One from Miami examined all chronic dialysis patients who started treatment in the first year of life. Of 52 patients, 20 (38%) died in the first year of life, mostly within the first month of life. Over up to 25 years of observation, the mortality totaled 54%. They did not report the gestational age of their patients, and no child was reported to be completely anephric.

The other study came from the University of Minnesota. It examined only infants started on peritoneal dialysis before 28 days of age (23 babies). Gestational age in this series ranged from 31-40 weeks (average 37 weeks) with 39% considered premature (<17 weeks of gestation). Survival at 1 year was 52%, with half of the deaths occurring before the infant could be discharged to home. Once again, no infant with complete absence of kidneys was reported.

Both studies confirm that getting these kids to an appropriate size for transplant (~10 kg body weight, generally at 15-18 months of age) can be a battle. Most children suffered infections and other problems leading to hospitalizations during that period. The Minnesota groups averaged 6 admissions each in the first year of life after neonatal discharge (average discharge occurred after 3 months of hospitalization, so those 6 re-admissions occurred within a 9-month period).

These infants also require support beyond dialysis and medications. Forced feedings via a tube were required in 94% of babies discharged on home dialysis in the Minnesota series.

The good news is that once these children get to transplant, they generally do as well as other children with end-stage kidney failure. Patient survival remains stable after 2 years of age, and the 5-year transplant graft survival rate is 83%, similar to that of older children transplanted in the same era.

Both of the studies discussed here started with infants on dialysis; we do not know how many parents chose not to pursue aggressive treatment for their critically ill offspring

Peritoneal dialysis allows us to save about half of the infants whose kidneys fail in the first months of life. However, these children often have multiple admissions over that first year of life, and they will be technology-dependent for their entire lives. All of these factors need to be weighed by the parents before embarking on infant dialysis. .

*Use of this illustration for 1 year online would cost me $282; click over to the Netter Illustration and view it with the watermark. You will get the general idea.

Uncommon Rocks

Kidney stones seem to be as common as rocks. A variety of factors can contribute to their formation, but sometimes an interesting cause can be identified. Protein in the urine can be a tip-off that something unusual is happening.

Dent’s Disease

This X-linked recessive disorder causes problems in the function of the kidneys’ proximal tubules, leading to:

  • Hypercalciuria (high urine calcium)
  • Nephrocalcinosis (calcium deposits in the kidney tissue)
  • Kidney stones (calcium crystals in the collecting system of the urinary tact)
  • Proteinuria (urine protein)
  • Rickets (poor bone mineralization)
  • Chronic kidney disease with loss of function

Because the disorder links to the X-chromosome, most affected patients are male. Girls may show mild signs and symptoms, but chronic kidney disease is rare.

In 60% of cases, a gene called CLC-5 shows a mutation. Abnormalities of OCRL1 cause another 15% of cases. The genetic cause is unknown in about one-quarter of patients who otherwise fit the diagnosis.

Click to Enlarge
Nephron: Click to Enlarge

Proximal Tubule Function

The kidneys receive about 20% of each heartbeat’s blood for filtration and removal of wastes. Most of this blood flows through special clumps of blood vessels that allow watery material from the blood to pass into Bowman’s Space, the first portion of the nephron. From there this filtrate enters the proximal tubule, the workhorse of the kidney. This part of the kidney retains most of the fluid and chemicals filtered into the nephron.

When I want to clean up the mess in a room, I pick up the trash and dispose of it. The kidney takes a different approach, instead sweeping everything in the room into the trash and then removing what it wishes to keep. The proximal tubule retains 2/3 to 3/4 of this good stuff for the kidney.

Severe proximal tubule dysfunction results in Fanconi Syndrome. The kidney wastes everything that it should retain, including bicarbonate, potassium, phosphate, protein, glucose, and calcium. In Dent’s disease the dysfunction is less severe. While excess urine calcium and protein is necessary for the diagnosis, phosphaturia and glucosuria are variable. Dent’s disease is ruled-out by the presence of renal tubular acidosis due to bicarbonate losses.

Prognosis

Affected boys often develop chronic progressive kidney disease, with 30-80% developing permanent kidney failure over time. Girls are generally asymptomatic carriers; if they have signs or symptoms, they are usually mild and cause no long-term kidney damage.

Treatment currently focuses on reducing stone risk through treatment of hypercalciuria with sodium restriction and thiazide diuretics. Other general treatments for chronic kidney disease should also be employed as necessary.

Upgrading

Greetings!

I am in the process of upgrading this website. I am finally ditching my GoDaddy Hosting Plan (and their ads that insult my intelligence). As you can see, I have my general info sheets over, and I’m bringing other content from the old site.

I have also provided the latest posts from my other online projects. WhizBANG! often contains adult language and themes, especially in the comments. I address science there, but also whatever random shiny object catches my eye. Academic Women for Equality Now! explores the lack of women in leadership in higher education, particularly in academic medicine.

Let me know if you have suggestions for the site. I am still figuring out this new place.