Introduction

One of the important functions of the kidneys is to aid in regulating and removing the toxins and waste products in the body.¹ Papillary necrosis is a condition in which the cells and tissues in the renal papillary in the kidneys die. This makes the kidneys ineffective in removing the waste products from the blood.² The renal papillae are necessary for the filtering flow of urine from the kidneys to the ureter through the opening of the collecting ducts.³ Papillary necrosis is characterised by the lesions on the renal papillary, which reduce the blood flow and is a form of nephropathy (kidney diseases).⁴

Overview of Papillary Necrosis

Causes and risk factors

Individuals can be at a higher risk of developing the condition if they suffer from any form of ischaemia, reducing the blood flow to the kidney tissues. These can be caused by analgesic abuse, pyelonephritis (kidney infection), urinary tract obstruction, tuberculosis, liver cirrhosis, thrombosis, and sickle cell disease.⁵ Patients with papillary necrosis often suffer from other multimorbidities, such as diabetes.⁶ Individuals can also be predisposed to the condition if they have a family history of kidney stones, which can become aggravated if they live a sedentary lifestyle.⁷ The condition also tends to develop later in life, and is most commonly diagnosed in adults over 50 years old. 

Analgesic use

Analgesics are medicines that can be used to help relieve pain. However, prolonged and continuous abuse of these medications can damage the kidneys. This is because the drugs increase blood pressure,⁸ damaging the filtering blood vessels in the kidneys. At the same time, they can stimulate the smooth muscle cells to grow, increasing the clogging in the arteries and reducing the blood flow in the kidneys.

Diabetes mellitus

Diabetes can cause the blood vessels needed for the tissue survival to die; this limits the kidney's ability and effectiveness to filter blood.⁹ In diabetes, the increased blood sugar levels can lead to a reduced elasticity in the blood vessels, creating a narrowing effect and reducing the blood flow. The nephrons needed to filter the waste products from the blood can be damaged from a prolonged lack of blood flow.¹⁰ Therefore, it can impair the functioning of the kidneys, as seen in papillary necrosis.

Urinary tract obstruction

The kidneys normally filter urine into the urinary tract; however, when there is a urinary tract obstruction, the renal papillae become vulnerable to ischaemia. This leads to the tissue deteriorating as the blood flow is reduced, impairing the waste product removal process.¹¹

Symptoms and diagnosis

This disease can result in the inability of the kidneys to concentrate urine. This can lead to symptoms such as:¹²

• Blood in urine
• Pain when urinating 
• Dark, red and cloudy urine
• Tissue particles in the urine 
• Incontinence 

Other symptoms may also include fever and chills. 

Impact of diet on Papillary Necrosis

Nutritional requirements

Foods that are high in potassium and phosphorus should be reduced. This is due to the kidneys being unable to remove the excess potassium in the blood.¹³ This increases the risk of hyperkalemia with high potassium levels in the blood, which impacts nerve transmission, cellular transport and the heart's contractions through potassium’s role in those processes.¹⁴ Additionally, excess phosphorus also needs to be removed from the blood by the kidneys. High levels of phosphorus in the blood causes the calcium in the bones to be removed, weakening them and increasing the risk of fractures and osteoporosis.¹⁵ When the kidneys are working harder to remove these, then further damage can be caused. Examples of foods high in potassium or phosphorus to avoid include):¹⁶

• Avocados
• Dark coloured soda
• Whole wheat bread
• Brown rice
• Bananas
• Dairy
• Oranges

Other foods high in potassium, such as canned and processed meats, should also be avoided. This is because a high salt intake increases the protein in the urine as well as reduces the amount of water removed, increasing the blood pressure.¹⁷ Therefore, straining the kidneys causes a greater decline in its function. Diets high in protein can also cause this as the waste byproducts from the protein digestion are built up in the blood rather than removed into the urine. The hyperfiltration required for these processes damages the kidneys.¹⁸

It is important to drink sufficient levels of fluid to reduce the risk of dehydration as it can lead to urine with a high concentration of minerals and waste products. This urine can result in the formation of crystals, which can create kidney stones.¹⁹ These increase the risk of renal papillary necrosis as the crystals build up the kidneys, which can create larger stones. The larger stones don’t pass through the urinary tract, causing pain and infections, worsening kidney damage. Staying hydrated aids in diluting the urine so that crystal formation doesn’t occur.²⁰

Antioxidant-rich foods

Further damage to the body as a result of renal papillary necrosis can be reduced by antioxidants. The antioxidants reduce the oxidative damage that the kidney disease can cause.²¹ Some examples of these include vitamins C, A and E, which are also often found in kidney dialysis treatment. They can be highlighted through the colours of fruit and vegetables, such as red or purple, which contain polyphenols and lycopene. Orange and yellow fruits and vegetables are a source of beta-carotene and flavonoids; green to white antioxidants include indoles, sulforaphanes, lutein and quercetin.²² A variety of sources including berries such as cranberries, blackberries, blueberries, and raspberries, as well as garlic, apples, peppers, and cabbage, are also recommended.

Case studies and research findings

Dietary interventions in patients

Patients may benefit from a specialised diet; this is organised with a dietician and can help to make sure health needs are met as well as meeting calorie targets. A low protein diet may be recommended; this may mean calories that would usually come from protein in the diet are replaced with fruits, vegetables and grains.²³ This supports energy levels as well as provides the fibre, vitamins, and minerals needed. Reductions in desserts using dairy, nuts, bananas, and chocolate are also recommended. This helps to reduce the intake of phosphorus- and calcium-containing foods. Commonly, with kidney diseases, the patients also suffer from anaemia, resulting in them requiring high levels of iron in their diets.²⁴ Sources of this include beef, pork, kidney beans, and iron-fortified cereals.

Studies supporting this include Lai et al.’s research into a low-protein and appropriate-calorie-intake diet. This also controlled the calcium, potassium, sodium and phosphorus intake throughout the diet. The outcomes showed that participants' plasma bicarbonate and vitamin D levels significantly increased (p = 0.004 and p = 0.03) alongside reductions in phosphorus concentration and C-reactive protein (p = 0.001 and p = 0.01).25 This provides evidence that this diet helps patients with reduced kidney functioning, as well as manages the symptoms and adverse effects to bone mineral density that may occur. Therefore reducing the cardiovascular risk and improving the metabolic profile and renal filtering.²⁶ 

Impact on kidney function and overall health

Changes in diet can improve kidney functioning, which allows for the effective filtering of blood, removing waste products. By aiding the chemical balance in the blood via the foods ingested, the risk of kidney failure is reduced.²⁷ This condition has no cure, but due to the multimorbidity often seen ^with it, better management with the use of painkillers and managing conditions such as diabetes can help prevent the condition from progressing into kidney failure. This requires a holistic approach to improving the quality of life and overall health.²⁸ This could be done through improvements in diet, an active lifestyle, and closely following the instructions of healthcare professionals when taking medications. 

Summary

The risk of renal papillary necrosis can be reduced through the dietary implementation of low protein, reduced dairy and calorie-controlled approaches. Patients would need an individualistic approach to their diet, which can be supported by a dietitian. They can also look at blood levels to understand the patient's current health condition and to plan future food intake. Furthermore, tracking the amount of fluids consumed within the day helps lower the risk of dehydration, which increases the risk of kidney stones.