Infectious acute tubulointerstitial nephritis

　　1. Etiology

　　Infectious ATIN is mainly seen in acute pyelonephritis and can also be caused by hemogenic infection. The most common cause is bacterial infection, followed by fungal, viral, and protozoan infections. In recent years, the increasing incidence of HIV infection caused by drug abuse and infectious acute tubulointerstitial nephritis caused by drug abuse in male reproductive organs has also become more common. The main causes of infectious ATIN include:

　　1. Bacteria: Escherichia coli, Paracoccus, Proteus, Mycobacteria, Staphylococcus, Klebsiella, Aerobacter, Alcaligenes, Pseudomonas aeruginosa, Streptococcus faecalis.

　　2. Spirochetes: Leptospira.

　　3. Fungi: Histoplasma.

　　4. Rickettsia.

　　5. Viruses: Cytomegalovirus, Han滩 virus, adenovirus, enterovirus.

　　Second, pathogenesis

　　Acute interstitial nephritis caused by systemic infection may not be due to direct invasion of the renal interstitium by bacteria, but rather immunological damage to the renal interstitium by bacteria or their toxins. Another possibility is that the infectious agent directly invades the renal interstitium, causing interstitial edema and neutrophil inflammatory infiltration, mainly in the renal medulla, while cortical inflammation is a characteristic of reactive tubulointerstitial nephritis. The interstitial damage caused by infectious ATIN induced by acute pyelonephritis is focal, with inflammatory foci radiating, which is significantly different from the pathological changes of reactive tubulointerstitial nephritis caused by systemic streptococcal infection. In the latter, infiltration surrounds the blood vessels in a ring-like manner, mainly concentrated in the cortex and the cortex-medulla junction. Acute pyelonephritis is an acute suppurative inflammation caused by direct invasion of the renal interstitium by bacteria, also known as acute suppurative interstitial nephritis. Common pathogenic bacteria include Escherichia coli, followed by Paracoccus, Proteus, and Pseudomonas aeruginosa. Factors that may trigger infection include urinary tract obstruction or other urinary tract abnormalities, pregnancy, advanced age, low immunity, and urinary dysfunction.

　　Severe cases may develop extensive hemorrhagic necrotic acute renal failure syndrome.

　　Acute renal failure, abbreviated as ARF, is a clinical emergency. The disease is caused by various etiologies and results in acute renal damage, leading to a rapid decrease in renal regulatory function within a few hours to a few days, which cannot maintain fluid and electrolyte balance and excrete metabolic products, resulting in hyperkalemia, metabolic acidosis, and acute uremic syndrome. This syndrome is clinically known as acute renal failure.

　　Clinically, it is mainly characterized by chills, high fever, elevated blood leukocytes, left shift, and systemic infectious symptoms, as well as renal tubular proteinuria, microscopic hematuria, leukocyteuria, casturia, and significant decreases in urine specific gravity and urine osmolality, indicating renal damage. Severe cases may develop acute renal failure syndrome. Unlike the renal damage in acute post-infectious glomerulonephritis, which appears 2 to 3 weeks after the pathogenic microorganism infection, the onset of infectious ATIN is earlier, usually in the initial days of infection, and occasionally after 10 to 12 days.

　　Infectious acute interstitial nephritis (ATIN) is most characteristic in clinical manifestations caused by acute pyelonephritis, where patients may suddenly develop fever, aversion to cold, renal area pain and tenderness, dysuria, and visible leukocyteuria, pyuria, and bacteriuria. Urine may contain casts, and urine culture is often positive.

　　Acute bacterial pyelonephritis generally does not cause a decrease in renal function, unless accompanied by or complicated with diabetes or urinary tract obstruction. When acute pyelonephritis causes ATIN, the common clinical manifestations are mild tubular function damage, with possible impairment of urine concentration and acidification function, which is usually reversible and can recover after infection control. Acute renal function impairment may be seen in infectious ATIN caused by hemorrhagic fever nephrosis, leptospirosis, brucellosis, and candidiasis. In underdeveloped areas, ATIN caused by acute bacterial pyelonephritis may occur widespread hemorrhagic necrosis of the renal parenchyma due to untimely treatment, leading to renal failure, but it is rare.

　　The proteinuria of infectious ATIN is mostly ~, the 24-hour urine protein is generally less than 2g, and proteinuria within the scope of nephropathy is uncommon.

　　Prognosis: Most ATIN related to drugs and infections is self-limiting. After identifying and removing possible pathogenic factors, the renal function of many cases improves within a few days. Even after controlling the infection, ATIN can be cured. Whether it can be completely cured is related to the duration of renal failure. Persistent and active tubulointerstitial inflammation is prone to lead to disease that cannot be cured and irreversible interstitial fibrosis. Another factor that may affect the prognosis is the extent and range of interstitial infiltration by mononuclear cells. If the factors that continue to invade cannot be removed, the patient may progress to end-stage renal disease.

　　The diagnostic methods are the same as those for urinary tract infections, the key is to differentiate between upper and lower urinary tract infections.

　　1. Urine tests:In patients with acute pyelonephritis, the urine antibody-coated test is positive, and leukocyteuria and (or) pyuria can be seen, as well as positive urine bacterial culture; in other infectious ATIN, leukocytes, red blood cell casts, and tubular proteinuria, microscopic hematuria, significant decrease in urine specific gravity and urine osmolality can be seen, urine culture is usually negative, urine NAG enzyme increases, and urine β2-m increases.

　　2. Blood tests:Increased blood leukocyte count, left shift of nuclear cells, and other systemic infectious symptoms, positive Tamm-Horsfall antibody, elevated IgG, azotemia and increased blood creatinine levels may occur when acute renal function impairment occurs. The most common serum electrolyte disorder is hyperkalemia, hyperchlorhydria, and hypocarboxyhemoglobinemia. Metabolic acidosis with hyperkalemia and hyperchlorhydria often appears before the GFR is severely reduced (less than 20ml/min). When the concentrating ability decreases, hypernatremia may occur. If the proximal tubular dysfunction worsens, metabolic acidosis with normal blood potassium levels, hypophosphatemia, and hypouricemia may occur.

　　3. Renal biopsy:The diagnosis and treatment options for acute interstitial nephritis are of great significance. Pathologically, the renal interstitium may show focal or diffuse inflammation, infiltration of monocytes, plasma cells, or polymorphonuclear cells, degeneration of renal tubular epithelial cells, and sometimes deposition of immune substances in the renal interstitium.

　　4. Special examinations such as B-ultrasound, KUB, and IVP show no morphological changes in the kidneys.

　　What is good for the body to eat for infectious acute tubulointerstitial nephritis?

　　1. Low-protein

　　The amount of supply should be determined according to the condition, with mild cases controlled at 20-40g/day to reduce the burden on the kidneys; the duration of a low-protein diet should not be too long to prevent anemia. Once blood urea nitrogen and creatinine clearance rates approach normal, regardless of whether there is proteinuria, the protein supply should gradually increase to 0.8g/kg per day to facilitate renal function recovery. Opt for high-quality proteins rich in essential amino acids and low in non-essential amino acids, such as eggs, milk, lean meat, and fish; it is not advisable to consume legumes and their products.

　　2. Limit sodium and water intake

　　At the onset of the disease, edema is the main symptom, as the kidneys cannot normally excrete water and sodium. Restricting fluid intake and avoiding salt are good methods to eliminate edema. The diet should be low in salt, without salt, or low in sodium according to the condition, urine output, and edema. A low-sodium diet should avoid adding salt or soy sauce and should also avoid foods high in sodium. For specific reference, see the dietary and nutritional treatment principles for heart failure and renal failure in Chapter 27.

　　3. Control potassium intake

　　During oliguria or anuria, the potassium intake should be strictly controlled, with water intake limited to less than 500ml/day, and high-potassium foods such as fresh mushrooms, shiitake mushrooms, jujubes, shellfish, beans, vegetables, and fruits should be avoided.

　　4. Energy

　　Treatment combines rest, medication, and dietary nutrition. Severe cases may require bed rest, thus reducing energy expenditure and decreasing appetite due to less activity. The daily energy supply does not need to be too high, with an appropriate range of 0.10-0.13MJ (25-30kcal)/kg, and the total daily energy should be around 6.69-8.37MJ (1600-2000kcal).

　　5. Carbohydrates and fats

　　Most of the dietary energy is provided by carbohydrates. Supplementing sufficient carbohydrates can prevent insufficient energy and ensure that the small amount of protein provided is used entirely for tissue repair and growth and development; it is advisable to add sweet pastries, vermicelli, and jelly to the diet. There is no need to strictly limit the total fat intake, but foods rich in animal fats and fried foods should be given less. Acute nephritis often accompanied by hypertension is not suitable for consuming a large amount of animal fats to prevent an increase in blood lipids; it is advisable to increase sweet pastries and vegetables high in carbohydrates, and the diet should be light in flavor.

　　6. Supply sufficient vitamins

　　Use fresh green leafy vegetables and fruits as much as possible. Fresh vegetables can enhance the appetite of patients, unless potassium is restricted during the oliguria phase, in which case vegetables should be limited; otherwise, fresh vegetables should be provided in abundance. During the recovery period, foods with nourishing properties such as yam, jujube, longan, lotus seeds, and silver ear can be supplied in greater quantities. Vitamin A, B-group vitamins, vitamin C, folic acid, vitamin B1, and iron are all beneficial for renal function recovery and the prevention of anemia, and should be adequately supplemented in the diet; foods such as sautéed cabbage with vinegar, scrambled eggs with tomatoes, and sautéed carrot shreds can be selected.

　　7. Increase the supply of alkaline foods

　　Acute glomerulonephritis causes acidic urine, and the acidity or alkalinity of food can regulate the urine pH value. Supplying alkaline foods can make the urine nearly neutral, which is beneficial for treatment. During the oliguria phase, fruits and vegetables rich in potassium should be limited to prevent the occurrence of hyperkalemia. Acidic foods refer to those that produce acidic substances after metabolism in the body, mainly including grains, beans, and protein-rich meat foods, while alkaline foods consist of vegetables, fruits, and dairy products, among others.

　　Two, Foods to avoid for infectious acute tubulointerstitial nephritis

　　1, Do not eat or eat less high-fat foods.Patients with chronic nephritis have symptoms of hypertension and anemia. Animal fats are an adverse factor for hypertension and anemia because fats can aggravate atherosclerosis and inhibit the function of hematopoiesis. Therefore, patients with chronic nephritis should not consume excessive amounts of animal fats. However, if there is no intake of fats in chronic nephritis, the body will become weaker. Therefore, in daily life, vegetable oils can be used instead, about 60 grams per day.

　　2, Do not eat high-sodium foods.The edema of chronic nephritis is greatly related to blood volume and sodium salt. Each gram of salt can bring in about 110 milliliters of water. If nephritis patients consume excessive salt and their urinary function is impaired, edema symptoms often worsen, blood volume increases, and heart failure can occur. Therefore, it is necessary to limit the intake of salt, and provide a low-sodium diet. The daily salt intake should be controlled below 2-4 grams to prevent the exacerbation of edema and the increase in blood volume, and to avoid accidents.

　　3, Limit the intake of foods high in purines and nitrogen.To reduce the burden on the kidneys, it is necessary to limit the intake of foods that stimulate kidney cells, such as spinach, celery, radish, beans, bean products, sardines, and chicken soup, fish soup, and meat soup. Because these foods contain a high amount of purines and nitrogen, their metabolic products cannot be excreted in time when renal function is poor, which has a negative impact on kidney function.

　　4, Avoid using strongly flavored seasonings.Strongly flavored seasonings such as pepper, mustard, garlic, and chili are harmful to kidney function and should be avoided. Since monosodium glutamate can cause thirst and a desire to drink water, it should also be used sparingly when restricting water intake.

　　5, Limit the intake of plant proteins.The amount of protein intake should be determined according to the condition of renal function. If the patient has oliguria, edema, hypertension, and nitrogen retention, the daily protein intake should be controlled at 20-40 grams to reduce the burden on the kidneys and avoid the accumulation of nitrogen in the body. In particular, plant proteins contain a large amount of purines, which can aggravate the intermediate metabolism of the kidneys, so it is not advisable to eat beans and bean products as nutritional supplements. Beans and bean products include soybeans, mung beans, broad beans, soy milk, tofu, etc.

　　Three, Dietetic recipe for infectious acute tubulointerstitial nephritis

　　1,鲤鱼赤豆饮: 1 large crucian carp, 60 grams of red beans, boil and eat the juice in one meal. Note that it should not be seasoned with salt. This recipe is suitable for patients with acute or chronic nephritis with significant edema and red and涩 urine.

　　2, Chicken with white pepper: 7 grains of white pepper, 1 fresh egg. First, make a small hole in the egg, then fill it with white pepper, seal the hole with flour, wrap it with wet paper, and steam it in a steamer until cooked. When served, peel off the shell and eat the egg with pepper together. Adults take 2 eggs per day, children take 1 egg per day. 10 days constitute a course of treatment, rest for 3 days after the first course, and then take the second course. It is suitable for chronic nephritis with deficiency of spleen and kidney, and deficiency of essence and blood.

　　33, Erjiao Soup 120 grams of red beans, 9 grams of Phytolacca acinosa, 1 day's dose, boil the soup and drink it, take for 3-5 days. Suitable for acute nephritis with wind-heat syndrome in the lung, damp-toxin accumulation.

　　32, Fishmoss and Plantago Decoction 60 grams of Houttuynia cordata, 60 grams of plantago, decocted with water and taken as a decoction. Suitable for nephritis with obvious edema and a yellow greasy tongue coating.

　　31, Red Bean and Mulberry Bark Decoction 60 grams of red beans, 15 grams of mulberry bark, decocted with water, remove the mulberry bark, drink the decoction and eat the beans. Suitable for chronic nephritis with slight edema on the surface and occasional pus cells in urine, as an adjuvant treatment, it is very suitable.

　　30, White茅Root Boiled Red Beans 250 grams of white mugwort root, 120 grams of red beans, boil with water until dry, remove the mugwort root, chew the beans in several doses, suitable for both acute and chronic nephritis.

　　29, Frog and Grasshopper Gourd Powder 2 dried frogs, 7 grasshoppers, 15 grams of dried gourd, slightly fried, ground into fine powder or made into pills, taken with warm wine, 6 grams each time, 3 times a day. Suitable for acute nephritis.

　　28, Crucian Carp Soup 500 grams of crucian carp, 1 head of garlic, 3 grams of black pepper, 3 grams of Sichuan pepper, 3 grams of dried tangerine peel, 3 grams of amomum villosum. Put scallion, sauce, salt, Sichuan pepper, garlic, etc. into the fish belly and cook into soup. Suitable for all types of chronic nephritis.

　　27, Honghua Seed Pork Soup 30 grams of Honghua seed, 120 grams of lean pork, decocted to drink the soup and eat the meat, 1 dose per day, taken twice. For the treatment of chronic nephritis edema and proteinuria, as well as for patients with spleen and kidney yang deficiency, water dampness泛滥, and spleen and kidney deficiency, essence and blood deficiency, it is suitable to eat.

　　26, Winter Melon and Carp Soup 500 grams of carp, 200 grams of winter melon (cut into pieces), cooked together, add 10 grams of scallion (small pieces) and a little salt before serving. Suitable for chronic nephritis patients to eat.

　　Prevention:It is mainly to actively treat symptoms for infections and systemic diseases caused by various reasons, prevent the occurrence of interstitial nephritis, and pay close attention to fluid and electrolyte imbalance for this disease. Appropriate strengthening of nutritional support therapy can prevent the occurrence of life-threatening complications such as acute renal failure, and take various measures to avoid factors that may worsen infection and promote gastrointestinal bleeding.