Systemic and Oral Health Manifestations of Kidney Disease

Chronic kidney disease (CKD) is the progressive loss of kidney function due to cumulative damage.¹ In the United States, approximately 37 million adults, or one in seven, have CKD, with nearly 90% of those cases remaining undiagnosed.^2,3 Socioeconomic status, race and ethnicity, lifestyle choices, and other systemic diseases all impact the incidence of CKD and end stage renal disease (ESRD).

Studies show that individuals of lower socioeconomic status have a higher incidence of CKD.⁴ Moreover, Black individuals are four times more likely to develop CKD than white individuals. Black Americans also have a higher prevalence of diabetes and hypertension, which both lead to CKD.² Lifestyle choices can influence the probability of CKD or ESRD. An unhealthy diet and physical inactivity are among the key modifiable risk factors for chronic conditions. Diabetes and high blood pressure are the most common causes of CKD in the United States.⁵

High blood pressure, swelling in the hands or feet, and blood in the urine are three early signs of CKD.⁶ Oral health professionals often assess and record blood pressure for all patients, providing an opportunity for referral if results are outside of the normal range. Patients are commonly referred for primary hypertension or essential hypertension, which accounts for about 95% of high-blood pressure cases.⁷ However, secondary hypertension is associated with undiagnosed chronic systemic conditions, such as CKD.

PHYSIOLOGY OF THE KIDNEYS

The kidneys control acid-base balance, water balance, electrolyte maintenance, toxin and waste product removal, blood pressure, production of the hormone erythropoietin, and activation of vitamin D.⁸ Kidneys maintain and regulate sodium, potassium, phosphorus, calcium and magnesium. Failure to filter out excess sodium contributes to hypertension and insulin resistance, which impacts urine output. Thus, one of the earliest signs of undiagnosed kidney disease is high blood pressure. An imbalance of potassium can lead to hyperkalemia, raising the risk for cardiac arrhythmia.^9–11 Decreased kidney function affects activation of vitamin D and the absorption of calcium, which may signal the parathyroid hormone. Increased levels of parathyroid can lead to osteoporosis, gastralgia and asthenia. Imbalance of minerals can cause bone demineralization of the jaw, decreased trabeculation, and reduced thickness of cortical bone, all of which could cause complications affecting osteointegration of dental implants, periodontal disease risk, and increased likelihood of jaw fracture.¹²

DIAGNOSIS

Routine blood and urine testing is important to diagnose CKD and assess the stage of disease progression. Blood tests are used to evaluate serum creatinine levels, glomerular filtration rate (GFR), and blood urea nitrogen (BUN).^13,14 Evaluating GFR levels provides a measure of kidney function and creatinine levels, whereas BUN tests measure the amount of urea nitrogen and the breakdown of protein in foods. Urine tests evaluate urinalysis, protein, microalbuminuria, and albumin-to-creatinine ratio. In Stage 3 CKD, individuals present with signs and symptoms, including fatigue, nausea, loss of appetite, fluid retention, shortness of breath, muscle cramps and dark urine.¹⁵

Preliminary research shows that measuring the level of creatinine in saliva may provide an early diagnostic tool for CKD.¹⁶ Salivary creatinine concentrations above 8.5 umol/l indicate the need for referral to a medical provider for additional testing.^16,17 Thus, saliva testing may help establish a diagnosis of CKD early, before clinical symptoms occur.

The dental management of patients with CKD is based on their stage in the disease process (Table 1), as CKD has five stages that are classified by the patient’s GFR. A GFR of 60 or higher is in the normal range. A GFR below 60 may mean kidney disease. A GFR of 15 or lower indicates kidney failure. In stages 1 and 2, many individuals do not experience any changes in their overall health. Some level of kidney damage is present at Stage 3, which has two substages: 3a (45 ml/min to 59 ml/min GFR) and 3b (30 ml/min to 44 ml/min GFR).¹⁵ In addition to the clinical symptoms of Stage 3, patients may report a metallic taste, oral malodor, difficulty concentrating, and numbness in toes and fingers.¹⁵ In Stage 4, the kidneys display advanced damage, signaling that patients will need dialysis and/or a kidney transplant. Stage 5 is referred to as ESRD, meaning there is need for long-term dialysis or a kidney transplant in order to maintain life.¹⁸

MEDICAL MANAGEMENT

For patients with ESRD, treatment includes hemodialysis, peritoneal dialysis and kidney transplant. Hemodialysis is scheduled three times/week at a hospital or dialysis center and the process requires three to four hours. Individuals undergoing hemodialysis must abide by strict dietary restrictions regarding the consumption of fluid, phosphorus, potassium and sodium. This population often experiences xerostomia due to fluid restrictions, and oral malodor because of reduced salivary flow, increasing their risk for mucosal lesions, such as candidiasis and dental caries, as well as alveolar bone loss and periodontal disease.¹⁹ Peritoneal dialysis removes waste products from the blood.²⁰ A catheter is placed in the abdomen, and treatment takes approximately eight to 10 hours per day.²⁰ Patients awaiting a kidney transplant often have an alkaline oral pH, causing increased accumulation of dental calculus.

Children with CKD may present with developmental defects of the enamel, tooth staining, stomatitis, gingivitis, gingival overgrowth, oral malodor, xerostomia and dysgeusia.^21,22 Among children with CKD, 31% to 83% will experience enamel hypoplasia due to their need for corticosteroid and tetracycline medications. Developmental defects of enamel increase the risk of caries and, as such, parents/caregivers should be educated on appropriate dietary choices and effective oral hygiene.

PHARMACOLOGY

The vast majority of prescribed medications and supplements are either metabolized by the kidneys or liver. Medications that are nephrotoxic, or those that may decrease renal blood flow, are contraindicated for patients with CKD.²³ If medications that are metabolized/excreted by the kidneys must be prescribed, their dosages and intervals may need to be adjusted.

In regard to dental pain management for patients with CKD, acetaminophen should be recommended. Based on the patient’s GFR, the dosing interval may need to be increased. Nonsteroidal anti-inflammatory drugs should be avoided, or the dosage reduced in patients with advanced renal failure due to their nephrotoxic and hypertensive effects.²⁴ For patients with CKD who have uremia, a condition in which the blood contains high levels of urea, aspirin should also be avoided because it will increase the risk of bleeding.

When treating an infection, the standard doses of penicillin, clindamycin and cephalosporin may be administered at prolonged dosing intervals, as needed. Dosage reductions are typically proportional to the degree of renal insufficiency.²³ Clinicians should consult with the patient’s nephrologist prior to treatment.²⁵

Gingival enlargement is common among patients with CKD due to their taking cyclosporine or calcium channel blockers. Cyclosporine is prescribed to help prevent acute rejection and the loss of the renal allograft. Calcium channel blockers are prescribed for patients with CKD-related hypertension. Dental lasers can be used to remove excess gingival tissue. Oral health professionals should inform a patient’s primary care provider about the presence of gingival enlargement in the hopes that alternative medications can be prescribed. If this is not possible, patients should be scheduled for more frequent recare intervals.

Patients with CKD who are receiving long-term adrenal-suppressive doses of corticosteroids may need additional prednisone before stressful, lengthy or invasive surgical procedures. The amount of prednisone necessary depends on the degree of suppression, along with the length and invasiveness of the surgery itself.²⁶ For example, procedures involving multiple extractions, bony impactions, periodontal surgery, bone resections, osteotomies, or any surgical procedure lasting longer than an hour should be supplemented with 10 to 20 mg of prednisone the day of the surgery and for at least one day postoperatively.²⁶

ORAL MANIFESTATIONS

Intraoral changes may occur in patients with CKD, such as uremic stomatitis, xerostomia, taste alterations, mucosal petechiae, ecchymosis, renal osteodystrophy and periodontal disease.^15,27 During routine dental visits, oral health professionals may note signs of undiagnosed CKD, such as uremic stomatitis, which is typically associated with untreated chronic renal failure. A painful lesion caused by elevated levels of urea nitrogen in the blood, uremic stomatitis may manifest in four forms: ulcerative, hemorrhagic, nonulcerative and hyperkeratotic. It may present with red mucosal ulcers or thick gray exudate covering the oral mucosa. Nonulcerative and hyperkeratotic types appear as white lesions. Hyperkeratotic lesions are more often found around the tongue and floor of the mouth. The pain associated with uremic stomatitis may be managed by using a mildly acidic mouthrinse (such as diluted hydrogen peroxide), sucking on ice chips, or applying topical anesthetics.¹⁵

Xerostomia and taste alterations commonly seen in patients with Stage 4 CKD are due to increased uremic levels in the salivary glands, which cause an ammonia-smelling odor or metallic taste due to the elevated pH. Petechiae and ecchymosis are caused by a decrease in platelet factor III, and are often found on the soft palate, tongue and buccal/labial mucosa.^15,27 Oral candidiasis affects 20% to 30% of patients with kidney transplants, and may be treated with topical antifungals,  such as nystatin, miconazole, gentian violet and amphotericin B.¹⁵

Renal osteodystrophy is a bone disease that occurs when the kidneys are unable to maintain proper levels of calcium, phosphorus and vitamin D, and may arise from parathyroid malfunction.¹⁵ Renal osteodystrophy causes “brown tumors” and loss of the lamina dura. In adults and children, renal osteodystrophy appears on X-rays as a ground glass appearance. It may lead to delayed tooth eruption, severe periodontal destruction and tooth mobility.¹⁵

DENTAL TEAM’S ROLE

Oral hygiene instruction should be emphasized pre- and post-kidney transplant. Pretransplant individuals are more prone to dry mouth and increased calcium due to the presence of uremia in their saliva. Prior to a kidney transplant, dental clearance should be obtained first and any teeth with a poor prognosis or periodontal abscess should be extracted.²¹ After the kidney transplant, individuals face an increased risk of dental caries and gingival enlargement due to their medication use. Oral hygiene instructions should be provided to reduce the risk of caries and oral infections and dental teams should offer specific strategies on how to decrease calculus accumulation.

Ninety percent of patients with CKD experience one or more of the following oral health conditions: xerostomia, oral malodor, uremic stomatitis, mucositis and glossitis.²⁸ Fluoride toothpastes, oral rinses and fluoride application should be recommended. Oral health professionals should be cautious in prescribing systemic fluoride supplements to children with CKD, however, because kidney impairment may cause fluoride retention.²¹ Dentists and dental hygienists can use caries risk assessment to assess, manage and select appropriate therapeutic aids for patients with CKD.

Progression of periodontitis in patients with CKD is based on host, environmental and bacteriological factors.²⁸ Patients with CKD have a higher concentration of urea, sodium and phosphate, in addition to a decreased salivary rate and buffering capacity. Reduced salivary flow increases the risk for calculus buildup, caries and periodontal disease.²⁹ Individuals with CKD may have loose or painful teeth due to their inability to absorb calcium properly.³⁰ Oral health professionals may recommend nonsurgical periodontal therapy to minimize the bacterial load and reduce inflammation, while monitoring bone levels and periodontal pockets.²⁸

Dental providers should also be mindful of oral lesions, taste changes and xerostomia linked to CKD or ESRD. Blood pressure screenings can improve patients’ awareness of their overall health and help clinicians make proper referrals to address kidney concerns. Early diagnosis of CKD is key to reducing the risk for further kidney damage and providing a wider variety of therapeutic options. For patients undergoing dialysis, dental treatment should be provided the day after dialysis. Premedications are given after recommendation by the patient’s physician or according to the American Heart Association guidelines.

CONCLUSION

For all patients, prevention is always the best management technique, and this includes baseline screenings, dietary counseling and tobacco cessation. Dental teams can educate patients on eating nutrient-rich foods and discuss the importance of exercise to help them achieve overall health.

In addition, interdisciplinary collaboration between dental and medical providers supports early diagnosis, proper treatment, and better outcomes in those with CKD. As patients often visit their oral health professional more frequently than their primary care provider, dentists and their teams may be the first to note signs of CKD, thus helping patients achieve the best possible outcomes.

REFERENCES

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From Decisions in Dentistry. November 2022;8(11)34-36, 39.