Calcoli Renali

Introduzione sui calcoli renali

Sebbene i calcoli renali siano una delle patologie più frequenti dell’era moderna, la loro esistenza era conosciuta sin dall’antichità. I progressi tecnologici e l’avvento di procedure sempre meno invasive hanno sicuramente rivoluzionato i metodi di rimozione dei calcoli ai reni.

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Tuttavia, le moderne tecniche endoscopiche non agiscono sulle cause della malattia ed hanno notevolmente aumentato i costi sanitari. Pertanto, oggigiorno, l’attenzione si è spostata sulla prevenzione della calcolosi renale che si basa essenzialmente su una corretta dieta.

Epidemiologia (torna su)

La prevalenza dei calcoli renali è compresa tra l’1% ed il 15% e può variare a seconda dell’età, del sesso, della razza e della distribuzione geografica.  L’aumento di frequenza di questa patologia è un fenomeno globale. I dati epidemiologici europei, giapponesi ed americani dimostrano che sia l’incidenza che la prevalenza dei calcoli ai reni sono in aumento in tutto il mondo.

Tale aumento è in parte dovuto anche all’ implementazione ed alla crescente diffusione di procedure diagnostiche quali l’ecografia e la TAC. Gli uomini sono affetti dai calcoli renali con una prevalenza di 2-3 volte superiore alle donne. Tale differenza è dovuta ad un effetto protettivo esercitato dagli estrogeni sulla formazione dei calcoli.

Tuttavia, negli ultimi anni, la differenza dell’incidenza di questa patologia nei due sessi si sta assottigliando. Negli Stati Uniti la popolazione di razza caucasica è più frequentemente colpita dai calcoli ai reni rispetto agli altri ceppi etnici (asiatici, ispanici ed afroamericani). I calcoli ai reni sono rari negli individui di età inferiore ai 20 anni ed il picco di incidenza si registra nella fascia di età compresa tra i 30 ed i 60 anni.

La maggiore prevalenza al mondo si registra nel sud est asiatico. Per quanto attiene i fattori geografici e climatici, i calcoli ai reni sono più frequenti nei climi caldi, nelle aree desertiche e tropicali e durante la stagione estiva. Alla base di questa differenza vi è la fisiologica riduzione della diuresi che avviene con il caldo ed il conseguente aumento di rischio di formazione di calcoli.

Per lo stesso motivo, altro fattore di rischio è rappresentato dallo svolgere un lavoro che costringe ad essere a contatto con alte temperature (cuochi, lavoratori dell’industria siderurgica etc.). Il principale fattore di rischio per i calcoli renali è l’obesità: maggiore l’indice di massa corporea di un individuo maggiore il rischio di formazione di calcoli ai reni. Tipicamente i soggetti obesi presentano un’aumentata secrezione di ossalati, acido urico, sodio e fosforo.

Altri fattori di rischio sono il diabete, la sindrome metabolica e le patologie cardiovascolari. Gli studi epidemiologici suggeriscono che la dieta ed i fattori ambientali hanno un ruolo predominante sui fattori genetici nel determinismo dei calcoli ai reni. Bere abbondanti quantità di acqua è invece un riconosciuto fattore protettivo per i calcoli renali.

Calcoli renali cause (torna su)

Vi sono particolari tipi di individui che hanno una elevata predisposizione a formare calcoli renali. Questi individui vengono definiti con termine inglese “stone formers”, ossia individui formanti calcoli. I processi chimico-fisici che portano alla formazione dei calcoli renali comprendono una cascata di eventi che si verifica quando il filtrato glomerulare attraversa il nefrone.

Calcoli renali diagnosi (torna su)

La valutazione diagnostica di un paziente affetto da sospetta calcolosi urinaria si basa su:

  • anamnesi
  • esame del sangue
  • esame delle urine
  • esami radiologici
  • analisi del calcolo
  • valutazione metabolica

All’ anamnesi l’urologo ricercherà eventuali condizioni predisponenti quali:

  • pregressi episodi di calcoli
  • anamnesi familiare positiva per calcolosi
  • malattie intestinali (in particolare diarrea cronica)
  • fratture patologiche
  • osteoporosi
  • infezioni urinarie ricorrenti associate a calcolosi infettiva
  • gotta
  • Rene solitario
  • Anomalie anatomiche
  • Insufficienza renale
  • Pregressa calcolosi di cistina, acido urico e/o struvite
  • Dieta a base di alimenti potenzialmente causa di calcoli
  • Assunzione di liquidi
  • Farmaci
  • Pregressi interventi per obesità (by pass gastrico)

Gli esami ematochimici permettono di rilevare la concentrazione nel sangue di:

  • Calcio
  • Ossalato
  • Cloro
  • Diossido di carbonio
  • Fosforo
  • Potassio
  • Acido urico
  • Azotemia
  • Creatinina
  • Paratormone (PTH)

La valutazione di questi parametri è di fondamentale importanza per comprendere le cause ed il tipo di calcoli.

All’ esame delle urine è possibile ricercare la presenza di cristalli nel sedimento urinario. Tramite il microscopio ottico l’analista valuta la forma dei cristalli, da cui si può risalire al tipo di calcoli di cui il paziente è affetto. Mediante l’urinocoltura si è in grado di ricercare la presenza di batteri produttori di ureasi potenziali causa di calcoli infettivi da struvite (Proteus, Klebsiella, Pseudomonas, Stafilococco).

Gli esami radiologici sono fondamentali per localizzare i calcoli renali e per avere informazioni sulla loro composizione. Solitamente vengono impiegati i seguenti esami:

  • Radiografia diretta
  • Ecografia apparato urinario
  • Urografia
  • TAC
Calcoli Renali
Calcoli renali

I calcoli ai reni possono essere radio-opachi o radiotrasparenti.

I calcoli radiopachi sono quelli a base di:

  • ossalato di calcio
  • fosfato di calcio
  • struvite
  • cistina

I calcoli radiotrasparenti sono:

  • acido urico
  • xantina
  • triamterene

Nel caso in cui si sospetti la presenza di un calcolo radiotrasparente sarà necessario eseguire una pieloureterografia oppure una TAC. Tramite l’imaging radiologico è inoltre possibile riconoscere eventuali anomalie anatomiche che predispongo alla calcolosi come una stenosi del giunto pieloureterale. In caso di episodio acuto (colica renale in atto) è preferibile non utilizzare esami che impiegano contrasti radiologici. In tali casi l’esame di scelta è l’ecografia, particolarmente utile per identificare uno stato di dilatazione degli ureteri e/o della pelvi renale (idronefrosi).

Laddove possibile, bisognerebbe sempre procedere con l’analisi microscopica del calcolo sia di tipo ottica che elettronica. Questo tipo di esame è in grado di stabilire con estrema precisione la composizione chimico-fisica dei calcoli espulsi spontaneamente o rimossi chirurgicamente.

Una valutazione metabolica estensiva si prefigge lo scopo di identificare l’alterazione e/o il processo patologico alla base della formazione di calcoli renali ed è fondamentale per impostare una corretta strategia di prevenzione nei confronti di potenziali futuri episodi di calcolosi.

La valutazione metabolica è indicata nei seguenti casi:

  • individui che sono affetti cronicamente da calcolosi (cosiddetti “stone formers”)
  • anamnesi familiare positiva per calcolosi
  • patologie intestinali (in particolare diarrea cronica)
  • fratture ossee patologiche
  • osteoporosi
  • infezioni urinarie ricorrenti associate a calcolosi
  • gotta
  • rene solitario
  • anomalie anatomiche
  • insufficienza renale
  • calcolosi da cistina, acido urico e/o struvite

Una valutazione metabolica estensiva prevede l’esecuzione di tutti gli esami già descritti con l’aggiunta dell’ esame delle urine raccolte nelle 24 ore. Questo esame consiste nella valutazione delle urine raccolte durante un’intera giornata tramite appositi contenitori.

Tramite lo studio delle urine nelle 24 ore si possono acquisire dettagliate informazioni sulla quantità totale di urine prodotte giornalmente, sulla concentrazione giornaliera di singole sostanze come proteine, elettroliti e amminoacidi.

Calcoli renali sintomi (torna su)

La maggior parte dei calcoli renali è di piccole dimensioni, non provoca sintomi e vengono espulsi spontaneamente. Di contro, calcoli di grosse dimensioni, possono causare una ostruzione urinaria e generare dolore.

La colica renale viene tipicamente riferita dal paziente come un dolore acuto che insorge al fianco, alla schiena e/o dell’addome inferiore. Il dolore spesso inizia improvvisamente e poi si sposta diventando più intenso col tempo.

 

Terapia (torna su)

Terapia medica conservativa

Esistono alcune misure preventive e raccomandazioni generali che sono molto utili per la prevenzione di qualsiasi tipo di calcolosi a prescindere dal tipo specifico dei calcoli.

Acqua per calcoli renali (torna su)

Una delle principali misure preventive della calcolosi è bere molto. L’assunzione di liquidi dovrebbe essere tale da generare un volume urinario giornaliero di almeno 2 litri. Una abbondante diuresi previene la stagnazione delle urine ed aumenta la diluizione di sostanze che, precipitando, possono portare alla formazione di calcoli.

In particolare è utile bere un tipo di acqua con un basso contenuto di elettroliti. Anche i succhi di agrumi, come la limonata e l’aranciata, assunti quotidianamente insieme con un adeguato apporto idrico, aumento il volume urinario e la citraturia.

Calcoli renali dieta (torna su)

È di fondamentale importanza per la prevenzione e la terapia dei calcoli renali una appropriata alimentazione. Una corretta alimentazione e l’attività fisica possono ridurre l’incidenza della calcolosi. Questo paragrafo intende pertanto rispondere all’ annoso interrogativo: “calcoli renali: cosa mangiare?”.

Studi epidemiologici eseguiti in diverse aree geografiche hanno dimostrato che i calcoli renali hanno una maggiore incidenza nelle popolazioni che hanno un aumentato consumo di proteine animali.

Calcoli renali rimedi (torna su)

Una volta eseguito un corretto iter diagnostico e verificata l’alterazione metabolica alla base della formazione dei calcoli, è possibile instaurare una corretta terapia medica. Grazie alla comprensione del meccanismo patologico alla base della formazione di calcoli (descritto nel capitolo “calcoli renali cause”), è possibile prescrivere programmi terapeutici basati su terapie selettive.

Tuttavia, se queste terapie iniziali non funzionano, come eliminare i calcoli renali? Tramite la terapia chirurgica è possibile rimuovere la maggiore quantità possibile di calcoli in un unico intervento minimizzando le complicanze.

Colica renale (torna su)

La colica renale è la manifestazione clinica più dolorosa della calcolosi. La colica renale è determinata dal passaggio dei calcoli dal rene nell’ uretere attraverso il giunto pielo-ureterale. I calcoli ureterali possono causare una ostruzione parziale o totale al decorso dell’urina.

Questa ostruzione aumenta la pressione nei dotti collettori del rene determinando una distensione della pelvi, dei calici e della capsula renale.

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