Made by DATEXIS (Data Science and Text-based Information Systems) at Beuth University of Applied Sciences Berlin
Deep Learning Technology: Sebastian Arnold, Betty van Aken, Paul Grundmann, Felix A. Gers and Alexander Löser. Learning Contextualized Document Representations for Healthcare Answer Retrieval. The Web Conference 2020 (WWW'20)
Funded by The Federal Ministry for Economic Affairs and Energy; Grant: 01MD19013D, Smart-MD Project, Digital Technologies
The disorder results in accumulation of the insoluble purine 2,8-dihydroxyadenine.
It can result in nephrolithiasis (kidney stones), acute renal failure and permanent kidney damage.
More than 300 individuals with this disease have been reported world-wide but it is not known how common this medical problem truly is. Patients with the disease deficiency lack the enzyme adenine phosphoribosyltransferase and therefore have difficulties breaking down dietary substances called purines, resulting in accumulation of a compound called 2,8-dihydroxyadenine (2,8-DHA) that is excreted by the kidneys. Up to 70% of affected patients, have red hair or relatives with this hair color.
Regular X-rays often fail to show the cystine stones, however they can be visualized in the diagnostic procedure that is called intravenous pyelogram (or IVP for short). Stones may show up on XR with a fuzzy gray appearance. They are radioopaque due to sulfur content, though more difficult to visualize than calcium oxalate stones.
Most patients with APRT deficiency have repeated episodes of kidney stones that are not detected by a conventional x-ray study. However, all stones are easily detected by other medical imaging methods such as ultrasound or computerized tomography (CT) scan. A minority of patients develop symptoms of kidney failure. Kidney stones are often associated with severe loin or abdominal pain. Symptoms associated with kidney failure are largely nonspecific such as increased fatigue and weakness, poor appetite, and weight loss. Children with the disease may have similar symptoms as adults. In young children, APRT deficiency can cause reddish-brown diaper spots.
Initial treatment is with adequate hydration, alkalization of the urine with citrate supplementation or acetazolamide, and dietary modification to reduce salt and protein intake (especially methionine). If this fails then patients are usually started on chelation therapy with an agent such as penicillamine. Tiopronin is another agent.
Once renal stones have formed, however, the first-line treatment is ESWL (Extracorporeal shock wave lithotripsy). If ESWL do not work efficiently surgery can be necessary. Both endoscopic surgery and conventional open-abdominal surgery have proven to be effective treatment modalities for patients with more advanced disease. Adequate hydration is the foremost aim of treatment to prevent cysteine stones. The goal is to increase the urine volume because the concentration of cystine in the urine is reduced which prevents cystine from precipitating from the urine and forming stones. People with cystine stones should consume 5 to 7 liters a day. The rationale behind alkalizing the urine is that cystine tends to stay in solution and causes no harm. In order to alkalize the urine, sodium biocarbonate has been used. One must be careful in alkalizing their urine because it could lead to other forms of stones in process of preventing cystine stones. Penicillamine is a drug that acts to form a complex with cystine that is 50 times more soluble than cystine itself. Percutaneous nephrolithotripsy (PNL) is performed via a port created by puncturing the kidney through the skin and enlarging the access port to 1 cm in diameter. Most of the time, cystine stones are too dense to be broken up by shock (ESWL) so PNL is needed.
Videos of surgery are available on various websites that show stone removal by percutaneous nephrolithotomy.
In February 2017, an article was published in Nature Medicine entitled 'Alpha lipoic acid treatment prevents cystine urolithiasis in a mouse model of cystinuria', suggesting that a high dose of the readily available antioxidant, alpha-lipoic acid at 2,700 mg/67 kg body weight daily reduced the incidence of stones. The effects were dose dependent. The results are unprecedented for cystinuria. A clinical trial is underway based on this mouse model.
In people with a history of stones, those who are less than 50 years of age and are presenting with the symptoms of stones without any concerning signs do not require helical CT scan imaging. A CT scan is also not typically recommended in children.
Otherwise a noncontrast helical CT scan with sections is the diagnostic modality of choice in the radiographic evaluation of suspected nephrolithiasis. All stones are detectable on CT scans except very rare stones composed of certain drug residues in the urine, such as from indinavir. Calcium-containing stones are relatively radiodense, and they can often be detected by a traditional radiograph of the abdomen that includes the kidneys, ureters, and bladder (KUB film). Some 60% of all renal stones are radiopaque. In general, calcium phosphate stones have the greatest density, followed by calcium oxalate and magnesium ammonium phosphate stones. Cystine calculi are only faintly radiodense, while uric acid stones are usually entirely radiolucent.
Where a CT scan is unavailable, an intravenous pyelogram may be performed to help confirm the diagnosis of urolithiasis. This involves intravenous injection of a contrast agent followed by a KUB film. Uroliths present in the kidneys, ureters or bladder may be better defined by the use of this contrast agent. Stones can also be detected by a retrograde pyelogram, where a similar contrast agent is injected directly into the distal ostium of the ureter (where the ureter terminates as it enters the bladder).
Renal ultrasonography can sometimes be useful, as it gives details about the presence of hydronephrosis, suggesting the stone is blocking the outflow of urine. Radiolucent stones, which do not appear on KUB, may show up on ultrasound imaging studies. Other advantages of renal ultrasonography include its low cost and absence of radiation exposure. Ultrasound imaging is useful for detecting stones in situations where X-rays or CT scans are discouraged, such as in children or pregnant women. Despite these advantages, renal ultrasonography in 2009 was not considered a substitute for noncontrast helical CT scan in the initial diagnostic evaluation of urolithiasis. The main reason for this is that compared with CT, renal ultrasonography more often fails to detect small stones (especially ureteral stones), as well as other serious disorders that could be causing the symptoms. A 2014 study confirmed that ultrasonography rather than CT as an initial diagnostic test results in less radiation exposure and did not find any significant complications.
Laboratory investigations typically carried out include:
- microscopic examination of the urine, which may show red blood cells, bacteria, leukocytes, urinary casts and crystals;
- urine culture to identify any infecting organisms present in the urinary tract and sensitivity to determine the susceptibility of these organisms to specific antibiotics;
- complete blood count, looking for neutrophilia (increased neutrophil granulocyte count) suggestive of bacterial infection, as seen in the setting of struvite stones;
- renal function tests to look for abnormally high blood calcium blood levels (hypercalcemia);
- 24 hour urine collection to measure total daily urinary volume, magnesium, sodium, uric acid, calcium, citrate, oxalate and phosphate;
- collection of stones (by urinating through a StoneScreen kidney stone collection cup or a simple tea strainer) is useful. Chemical analysis of collected stones can establish their composition, which in turn can help to guide future preventive and therapeutic management.
Diagnostic workup varies by the stone type, but in general:
- Clinical history and physical examination
- Imaging studies
- Some stone types (mainly those with substantial calcium content) can be detected on X-ray and CT scan
- Many stone types can be detected by ultrasound
- Factors contributing to stone formation (as in #Etiology) are often tested:
- Laboratory testing can give levels of relevant substances in blood or urine
- Some stones can be directly recovered (at surgery, or when they leave the body spontaneously) and sent to a laboratory for analysis of content
Diagnosis is based on results of bladder catheterization, ultrasonography, CT scan, cystourethroscopy, or pyelography, depending on the level of obstruction.
Treatment, depending on cause, may require prompt drainage of the bladder via catheterization, medical instrumentation, surgery (e.g., endoscopy, lithotripsy), hormonal therapy, or a combination of these modalities.
Treatment of the obstruction at the level of the ureter:
Modification of predisposing factors can sometimes slow or reverse stone formation. Treatment varies by stone type, but, in general:
- Medication
- Surgery (lithotomy)
- Antibiotics and/or surgery for infections
- Medication
- Extracorporeal shock wave lithotripsy (ESWL) for removal of calculi
Many other complications arise from ureteroceles. Redundant collection systems are usually smaller in diameter than single, and predispose the patient to impassable kidney stones. The effective "bladder within a bladder" compounds this problem by increasing the collision of uric acid particles, the process by which uric acid stones are formed. Ureterocele is also associated with poor kidney function. It can cause frequent blockage of the ureter leading to serious kidney damage. In other cases, a small, upper portion of the kidney is congenitally non-functional. Though often benign, this problem can necessitate the removal of non-functioning parts.
Definitive causes of ureterocele have not been found. While the abnormal growth occurs within the uterus, it has not been substantiated that genetics are to blame.
The disease is chronic and often progresses slowly. Prognosis is generally poor when associated with glaucoma [1,2].
Penetrating karatoplasty and endothelial keratoplasty can be used as treatments for severe cases of ICE [2,8]. Because glaucoma and elevated intraocular pressure are often present in ICE patients, long term follow up may be needed to ensure adequate intraocular pressures are maintained [2,7]